More than 800 species of freshwater fishes are precious biological resources in the inland water system of China. Among them, there are a great number of endemic and otherwise precious forms, and many monotypic genera and species. Recently, owing to a combination of natural and human-caused events, many of these fishes have gradually become endangered. Preliminary results indicate that 92 species of fish in China are endangered, and these account for 10% of the total freshwater fishes in China. For the purpose of protection of the biodiversity of fishes, it is necessary to analyse the causes which have led the fishes to become endangered. This report could be used as a scientific reference for researching and saving the endemic precious freshwater fishes in China.

Key words: Endangered freshwater fishes, Causes of Endangerment, China

In the process of the evolution of living things, along with the origin of life, the extinction of life also existed. In the long history of life, speciation and extinction of living things often kept a relative balance. Over time, especially as a result of the impact of the activities of human beings, this natural pattern of biodiversity has been altered. Finally, in modern society, the activities of humans have not only accelerated the progress of society and the development of human-based economies, but also have become a major source of disturbance to other species. Human influences upon nature happened all around the globe and are the main factor of the extinction of living things (Solbrig, 1992).

The same as other living things, the life of freshwater fishes is influenced by human activity. Economic growth and production has resulted in significant changes to the environment, so that some regional fishes of economic importance have become endangered within several decades of unsustainable use. And the structure of most fish populations has become small sized and lower-aged. At the present time, not only has the total number freshwater fishes declined, but the number of species of fish has also decreased.

As a result of the many different geographical environments in China, there is a very great biodiversity of freshwater fishes (about 900 species). This biodiversity is a precious biological resource in the inland water system of China. This biodiversity is comprised of 70% cyprinid fishes, as well as significant numbers of endemic and precious groups. Many of the forms are of monotypic genera and monotypic species. These fishes are special and precious research material to enhance our understanding of phylogenetics and biogeography. And they represent a very important biological resource for humans. But over the past several decades, many of these forms have become endangered or extinct. Preliminary results indicate that 92 species of Chinese freshwater fishes are endangered, and these account for 10% of the total freshwater fishes in China (Fig. 1). Among them, 52 species are cyprinid fishes, 11 are catfishes fishes, 5 are sturgeons, 6 are salmon and 18 species belong to other taxonomic groups of fishes (Tab.1 and Fig. 2). The degree of imminent danger to these threatened forms may be divided into 4 grades: extinct, rare, endangered and gradual endangered. In Chinese freshwater fishes, 4 species are extinct, 23 species are rare, 28 species are endangered and 37 species are gradual endangered (Fig.3).

Table 1. The statistics of endangered freshwater fishes in China

Figure 1. The percentage of endangered freshwater fishes in China

Figure 2. The statistics of the endangered Chinese freshwater fishes

Figure 3. The statistics of the endangered grade of Chinese freshwater fishes

Table 2. The list of the endangered freshwater fishes in China

EEL: 1-2

1. Lampetra reissneri (Dybowsky)

2. Lampetra japonica (Martens)

STURGEON: 3-7

3. Acipenser schrencki (Brandt)

4. Acipenser dabryanus Dumeril

5. Acipenser sinensis Gray

6. Huso dauricus (Georgi)

7. Psephurus gladius (Martens)

8. Macrura reevesi (Richardson)

SALMONS: 9-15

9. Oncorhynchus masou formosanus (Jordan et Oshima)

10. Hucho taimen (Pallas)

11. Hucho bleekeri Kimura

12. Brachymystax lenok tsinlingensis Li

13. Stenodus leucichthys nelma (Pallas)

14. Coregonus ussuriensis Berg

15. Thymallus arcticus grubei Dybowsky

16. Plecoglossus altivelis Temminck et Schlegel

17. Anguilla marmorata Quoy et Gaimard

18. Gyrinocheilus aymonieri (Tirant)

SUCKER: 19

19. Myxocyprinus asiaticus (Bleeker)

CYPRINID: 20-71

20. Candidia barbutus (Regan)

21. Parazacco spilurus (Günther)

22. Zacco chengdui Kimura

23. Tanichthys albonubes Lin

24. Aphyocypris pooni Lin

25 Gobiocypris rarus Ye et Fu

26. Luciobrama macrocephalus (Lacepede)

27. Leuciscus merzbacheri (Zugmayer)

28. Atrilinea roulei (Wu)

29. Macrochirichthys macrochirius (Cuvier et Valenciennes)

30. Rasborinus formosae Oshima

31. Pogobrama barbatula (Luo et Huang)

32. Anabarilius alburnops (Regan)

33. Hainania serrata Koller

34. Xenocypris yunnanensis Nichols

35. Xenocyprinoides parvulus Chen

36. Hampala macrolepidota van Hasselt

37. Sinocyclocheilus grahami (Regan)

38. Sinocyclocheilus anophthalmua Chen et Chu

39. Typhlobarbus nudiventris Chu et Chen

40. Luciocyprinus langsori Vaillant

41. Cosmochilus cardinalis Chu et Roberts

42. Scaphesthes alticorpus Oshima

43. Parator zonatus (Lin)

44. Balantiocheilus hekouensis Wu

45. Epalzeorhynchus bicornis Wu

46. Semilabeo obseurus Lin

47. Ptychidio macrops Fang

48. Sinocrossocheilus guizhouensis Wu

49. Placocheilus cryptonemus Cui et Li

50. Pseudorasbora elongata Wu

51. Squalidus minor (Harada)

52. Coreius septentrionalis (Nichols)

53. Platysmacheilus longibarbatus Lo, Yao et Chen

54. Schizothorax biddulphi Günther

55. Schizothorax taliensis Regan

56. Aspiorhynchus laticeps (Day)

57. Diptychus kaznakovi (Nichosky)

58. Oxygymnocypris stewartii (Lloyd)

59. Chuanchia labiosa Herzenstein

60. Platypharodon extremus Herzenstein

61. Puntioplites proctozysron (Bleeker)

62. Procypris merus Lin

63. Procypris rabaudi (Tchang)

64. Cyprinus micristius Regan

65. Cyprinus yilongensis Yang et al.

66. Cyprinus megalophthalmus Wu et al.

67. Cyprinus longipectoralis Chen et Hwang

68. Cyprinus pellegrini Tchang

69. Cyprinus yunnanensis Tchang

70. Cyprinus ilishaestomus Chen et Hwang

71. Gobiobotia homalopteroidea Rendahl

72. Psilorhynchus homaloptera Hora et Mukerji

COBITID: 73-76

73. Oreonectes anophthalmus Zheng

74. Noemacheilus gejiuensis (Chu et Chen)

75. Triplophysa siluroides (Herzenstein)

76. Leptobotia elongata (Bleeker)

77. Plesiomyzon baotingensis Zheng et Chen

78. Protomyzon pachycheilus Chen

CATFISHES: 79-89

79. Silurus soldatovi Nikolsky et Soin

80. Silurus mento Regan

81. Kryptopterus moorei Smith

82. Sinopangasius semicuitratus Chang et Wu

83. Pangasius sanitwangsei Smith

84. Cranoglanis bouderius (Richardson)

85. Akysis brachybarbatus Chen

86. Pseudobagrus madianalis (Regan)

87. Liobagrus kingi Tchang

88. Bagarius bagarius (Hamilton)

89. Gagata cenia (Hamilton)

90. Coresiniperca roulei (Wu)

91. Trichogaster trichopterus (Pallas)

92. Trachidermus fasciatus Heckel

II. Causes of endangerment of the freshwater fishes in China

1. Alteration of fish habitat

Although there may be many different reasons for endangerment of species of flora and fauna, the most conspicuous reason is the change and loss of habitat for living things. For the fishes, the main factors of endangerment are changes of environment caused by the construction of hydroelectric projects, excessive exploitation of fishery resources, pollution of water systems, unchecked introduction of non-native fish species, and incomplete regulation of the sustainable yield of fisheries (Walter et al. 1993).

1.1 The construction of water conservation projects (the dams of hydroelectric projects)

After construction of hydroelectirc dams, the natural environment of rivers changes enormously. The changes caused by the dams form many stress for fishes, so that they can not adapt to the new conditions. For example, after the construction of dams, running water habitats are changed to those of still water. As a result, running water fishes can not survive. The most serious effect of dam-building to fishes is the change of their reproductive environment. Also, dams can cut off the migration routes of fishes, which in turn directly effects their growth and reproduction, and limits the distribution of their population. In turn, these effects severely compromise the genetic resources of species.

Recently in China, for the purpose of hydroelectric power and irrigation, many dams are being built in stems and branches of rivers. For example, on the Changjiang River, the Gezhouba dam and the Three-gorges dam are in the process of being built. These projects will certainly change the fish habitat and deeply influence the structure of the fish populations and their reproduction. The reproduction and growth of the Chinese sturgeon was deeply influenced by these projects.

1.2 The reclaiming of land from lakes and rivers

The reduction of the area of rivers and lakes is the main problem for the preservation of fish populations in China recently. Human economic activity greatly increases the requirement for grains. For this purpose, people build dikes on the rivers and lakes. The dike-building eliminates shallow areas of rivers and lakes. This action results in reduction of the living space for fishes and other aquatic life. Fish populations also are reduced greatly. These projects are often built around lakes, so that they are more harmful to lake fishes.

1.3 Natural catastrophe

Natural catastrophes may also be one of the reasons for environmental changes. Destruction of forest and vegetation often causes mountain torrents in the upper reaches of rivers, and the floods can carry great amounts of soil and sands into rivers. This errosion must directly influence the fish respiration. This condition often causes the death of great number of fishes.

The construction of dams often causes damage to or the disappearance of fish spawning areas in rivers. Because most river fishes have a fixed spawning area, if a dam cuts off river current, their spawning area is inevitably damaged or relocated. Also, pollution caused by industry and other sources can cause damage to fish spawning areas. This condition must limit significantly the reproduction and stability of fish populations. Damage to water plants which are essential in the diet of fishes may further negatively influence the habitat and ability to reproduce of fishes. At the same time, the population of plant-eating fishes may decrease or disappear.

3.1 The excessive fishery

The increase of the human population results in the need for increased production of food. As a result, fish have frequently been over-exploited as food. Such non-sustainable harvesting is one of the very important reasons for the decline of freshwater fishes in China. Excessive exploitation has greatly reduced fish populations in all Chinese rivers and lakes. Many fishes which formerly had economic status have become rare species or endangered. Examples are Macrura reevesi (Richardson) and Trachidermus fasiatus Heckel. Because of overexploitation of the fishery in earlier times, now in the Changjiang River the production of economic fishes has been decreased to a very small scale. In addition, the number of professional fishman has decreased greatly because there are not enough commerically available fishes in the Changjiang River.

3.2 Unchecked elimination of carnivorous fishes from lakes

For the purpose of aquaculture in lakes, people have often removed all carnivorous fishes from lakes. This method sometimes can increase fish production in the short term, but it can also damage the biodiversity and ecosystem of lakes. The result is fewer fish species, and fish populations that are of small-size and young-aged individuals in lakes. Elopichthys bambusa and Erythriculterid are often removed from fish-farming areas, but at the same time, other different species also are eliminated.

3.3 Mass capture of fishes

This fishery technique includes the capture of a mass of parent, juvenile, larva and overwintering fishes. Recently, this harmful fishery technique has become more and more widely used. Unchecked capture of all-aged fishes often influences the balance of fish populations, and this obstructs the replenishment of fry. The result is a greatly decreased population of fishes.

3.4 Special fishery techniques

Some current fishery techniques used in rivers and lakes catch all-sized and all-aged fishes, including the larva and juvenile fishes. These fishery techniques seriously limit the development of fish populations and fatally damage native fish resources. Some water birds and otters are often used as the tools of the fishery, and these animals often catch fishes of any small size, especially the juvenile and larva.

Along with the development of industry, agriculture and capital construction, more and more industrial wastes and farm chemicals are being poured into rivers and lakes. This pollution directly influences the respiration of fishes. These wastes seriously pollute the aquatic environment for fishes, so that the living space of fishes becomes smaller and smaller.

Introduction of non-native fishes often causes damage to the balance among fishes in the same water system. At times the introduced and native species may occupy the same ecological niche. This condition often results in the extinction of endemic species. Some introduced fish species have more powerful adaptive capacity. They can occupy all of the niche so that the endemic species is unable to obtain sufficient living space and food. The typical example is that of the introduction of perch (Perca fluviatilis Linnaeus) from the Erqisi River into the Bosten River. This introduction led to the extinction of the schizothoracin (Aspiorhynchus laticeps (Day)).

In China, there are many regulations for the protection of fish resources. Also, there are many which limit the exploitation of a fishery. In reality, however, the execution of these regulations is very difficult in some areas. To change this condition, public relation propaganda and education are necessary.