by
K.F. Walker
Department of Zoology, University of Adelaide, South Australia 5005, Australia
and
H.Z. Yang
Bureau of Aquatic Products, Xining, Qinghai 810001, People's Republic of China
The remote provinces of Qinghai, Xinjiang and Xizang (Tibet) in western China have fishery potential that is small by world standards, but significant nonetheless. Although the region is arid and cold (altitude >3000 m) there are many lakes and rivers fed by runoff from nearby mountains, and the region supports 190 fish species, notably the native naked carp (or "snow trout"; Cyprinidae: Schizothoracinae). Fisheries have been established for more than 30 years, but contribute less than 0.2% of agricultural production. A growing population (21 million) has encouraged the expansion of capture fisheries and aquaculture.
Large-scale fishing in several lakes began in 1958. Production followed a typical pattern, with high initial yields later declining as the larger fish were removed. After 1978 operations were rationalised by the introduction of Fishery Management Stations. There is potential for development of regional capture fisheries, although the viability of existing fisheries depends on management. There is limited aquaculture in Qinghai (100 t in 1990) and none in Xizang, but in Xinjiang production (6000 t in 1990) has exceeded that of capture fisheries since 1986. Stocking of reservoirs with fingerlings of cyprinids and other species has been highly successful, and aquaculture is likely to expand in the future, particularly for cold-tolerant species like rainbow trout (Oncorhynchus mykiss).
Brief case histories are provided for the two major lake fisheries. The Qinghai Lake fishery for the endemic naked carp (Gymnocypris przewalskii) was opened to commercial exploitation in 1958. Trawler catches peaked at 28,000 t in 1961 and declined until about 1970, when they became more stable. In 1990 the legal annual catch is about 2000 t (including a 1200 t factory quota), with perhaps another 1700 t lost to unauthorised fishing and piscivorous birds. Naked carp are slow-growing (0.5 kg in 10 years) and the population would take a long time to recover from over-exploitation. Changes in management are required because the trawler catch includes many immature fish, and because the fish spawning areas are being degraded. There is also scope for increasing the value of naked carp through improved handling, processing and marketing. The Bosten Lake fishery in Xinjiang produces an annual catch of about 2000 t, dominated by perch (Perca fluviatilis). Management changes have been imposed to protect spawning populations and to protect cyprinids against predation by perch.
Qinghai, Xinjiang and Xizang (Tibet) are the three westernmost provinces of China, covering 3.62 million km2 or about 40% of the country (Fig. 1). They are neighbours to Afghanistan, Tajikistan, Kyrgyzstan, Kazakhstan, the Russian Federation and Mongolia in the west and north, and India, Bhutan, Nepal and Pakistan in the south. The region is mountainous, bounded by the Himalayas to the south and the Karakoram to the west, and divided by the Kunlun Mountains, separating Xinjiang from the Qinghai-Xizang Plateau ("The Roof of Asia", average altitude >4000 m above sea level). The Tien Shan Mountains further divide Xinjiang into northern and southern halves. Southern Xinjiang includes the Turpan Depression and Lake Aiding (154 m below sea level), the lowest point in China.
The rugged landscape and harsh climate of this remote area support a human population of about 21 million. Although travellers have visited the region since the 19th century, it was not until after the People's Republic was founded in 1949 that comprehensive investigations began of its natural resources (e.g. Li, 1959; Academia Sinica, 1975, 1979; Anon., 1981). Most of the published records are in Chinese, however, and not easily accessible to scientists in other countries.
Although the region is mainly arid, many large rivers including the Brahmaputra (Yarlung Zangbo), Mekong (Lancang), Yangtse (Changjiang) and Yellow (Huanghe) originate on the nearby slopes of the Himalayas. Runoff from the mountains amounts to 608 km3, or more than 70% of China's total water resources. The total lake area exceeds 40,000 km2, including 10 of the 22 Chinese lakes with areas greater than 500 km2 (Wang, 1987). There are many diverse freshwater and saline environments, including underground waters and springs, and water pollution is insignificant. The region therefore has ample resources to sustain fisheries development, particularly for cold-tolerant species.
This chapter is drawn partly from a program of research and development, Fisheries Development in Qinghai Province, undertaken in 1989-92 by the Chinese Government with assistance from the United Nations Development Program and the Food and Agriculture Organization of the United Nations (Edwards, 1992; Walker et al., 1996). The chapter outlines the status of fisheries in Qinghai, Xinjiang and Xizang, and provides case histories for two important fisheries, Qinghai Lake (Qinghai) and Bosten Lake (Xinjiang).
2.1 Climate
The region has a desert climate, strongly influenced by altitude (Köppen classification BW; see also Liu, 1980; Liu et al.,1989; Wang, 1987; Williams, 1991). On the Qinghai-Xizang Plateau the average minimum monthly temperatures range from -10 to -15°C, and the mean summer maxima of 15-20°C are similar to winter temperatures at sea level in the same latitudes. In northern Xinjiang average temperatures range from -18°C in January to 28°C in July, although the extreme temperatures recorded for all China (-51.5, 48.9°C) are also from this area. Annual precipitation ranges from 600-1000 mm on the northern slopes of the
Himalayas to 20-100 mm on either side of the Kunlun Mountains, and evaporation is 2500-3500 mm. In Xinjiang the mean annual precipitation is 150 mm and evaporation is 1600-4400 mm. Annual sunshine averages 3000 h, some 50-100% more than in lowland areas at similar latitudes.
2.2 Limnology
Information on the lakes and rivers that support the principal regional fisheries is shown in Tables 1-3. A limnological overview of the region is given by Williams (1991), and a comprehensive report on Qinghai Lake, the largest lake in China, is provided by Academia Sinica (1979) (see also Melack, 1983; Kelts et al., 1989; Walker et al., 1996).
The largest lakes include Qinghai (Qinghai Hu), Gyaring (Zhalin), Ngoring (Elin) and Keluke in Qinghai Province, Bosten, Ulungur, Ebinur and Sayram (Shailimu) in Xinjiang Province and Yamdrok, Namucuo and Banggong in Xizang Province (Fig. 1, Table 1). Small lakes are common and may be permanent or ephemeral, depending on local precipitation and their proximity to rivers. Polymictic circulation patterns prevail in the shallow lakes, but the deeper ones tend to be dimictic. Salinities range from fresh water to crystallising brines, and the water chemistry is predominantly sodium chloride although calcium, magnesium, bicarbonate, carbonate and sulphate are important in some instances. Values of pH generally are high, and often above 9.0. Plant nutrient concentrations are variable in waters throughout the region, perhaps reflecting land use, and the lakes range accordingly from oligotrophic to eutrophic status. Typical standing crops of benthos, macrophytes, phytoplankton and zooplankton asociated with some lake fisheries are shown in Table 2.
Table 3 shows data for eight rivers important as fisheries. There have been few investigations of river water quality other than for the Yellow River (see below). Water chemistry depends upon local peculiarities of climate, geology and topography, and is increasingly affected by agricultural, domestic and industrial pollution. There are signs of salinization, but the consequences are manifest mainly in areas further downstream, outside the region. Sediment loads appear to be high, mainly as a result of agricultural activities, but there are few supporting data.
In the Yellow River as a whole, thousands of discrete pollution sources have been catalogued and water quality generally does not meet fishery standards. In the lower and middle reaches, levels of arsenic, cyanide, mercury and phenol are well above levels toxic to fish and other animals. Data for the upper reaches in Qinghai are given by He et al. (1986). Typical Secchi transparencies are 20-32 cm, dissolved oxygen 6-8 mg l-1, pH 8.0-8.7 and hardness and alkalinity 2.68-3.68 and 2.21-5.00 mg l-1, respectively. Salinities are 227-340 mg l-1, and major ions include calcium (37.0-42.6 mg l-1), magnesium (8.4-18.7), sodium and potassium (combined: 6.9-34.0), bicarbonate (154-187), chloride (9.3-37.0) and sulphate (8.8-18.8). There are some supporting data for nutrients, including phosphorus (0.002-0.017 mg
l-1), nitrogen (nitrite 0.002-0.004, nitrate 0.037-0.30, ammonium 0.037-0.421) and silica (4.2-8.0).
2.3 Biological basis for fish production
In a review of work in Qinghai over the past 40 years, Wang (1987) noted 78 species of phytoplankton, dominated by more than 20 genera of Bacillariophyta and Chlorophyta. He also noted 60 zooplankton species, dominated by Arctodiaptomus denticornis (Copepoda), Hexarthra fennica (Rotifera) and Moina rectirostris (Cladocera), and 32 benthic species, primarily Chironomidae (Diptera). Fish biomass equivalents (kg ha-1) of plankton, benthos and macrophytes in four lakes are shown in Table 4. Note that by convention in China the potential fish biomass is estimated by assuming biomass-conversion efficiencies of 1/3 for phytoplankton, 1/2 for zooplankton and 1/6 for benthos. For example, a benthic biomass of 600 kg ha-1 would have an estimated equivalent fish biomass of 100 kg ha-1.
In Xinjiang the most recent investigation has been a survey of 36 diverse environments in 1985-87 by Liu et al. (1989). They recorded 157 species of phytoplankton, including 60 Bacillariophyta (predominantly Cyclotella, Navicula and Synedra) and 53 Chlorophyta (Ankistrodesmus, Oocystis, Scenedesmus). Standing crops averaged 3.11 million (range 5-10 million) cells l-1 or 3.353 (0.029-15.888) mg l-1. Zooplankton species numbered 76, including 26 protozoan (Cyclidium, Strombidium, Tintinnidium), 10 copepod (Arctodiaptomus salinus, Cyclops vicinus vicinus), 15 cladoceran (Bosmina longirostris, Diaphanosoma brachyurum) and 25 rotifer species (Keratella cochlearis, Polyarthra euryptera). Standing crops averaged 6263 (29-39,977) organisms l-1, with biomass 1.7624 (0.043-10.869) mg l-1 and an equivalent fish biomass 55 (1.2-266) kg ha-1. The benthos included 130 species, including oligochaetes (3 families, 9 genera and 18 species, or 14% of all benthic species), insects (28, 59, 88, 68%) and molluscs (5, 7, 15, 6%). Dominant species were Tubifex tubifex and Limnodrilus helveticus (Oligochaeta), Procladius choreus, Cryptochironomus digitatus, C. conjugens and Chironomus plumosus (Diptera: Chironomidae) and Gyraulus albus, Radix peregra and R. swinhoei (Mollusca). The average benthic biomass was 1943 organisms m-2 (12.587 g m-2), including 7.673 g m-2 molluscan biomass and 1.073 g m-2 oligochaete biomass, with an equivalent fish biomass of 8.2 kg ha-1. Macrophytes were represented by 107 species (30 families), notably Acorus calamus, Phragmites communis, Myriophyllum ussuriense, Potamogeton pectinatus and P. malaiannus. The average biomass was 440 (17-3298) g m-2 and equivalent fish biomass 59.7 (13.8-130.5) kg ha-1.
There are no systematic data for plants or invertebrates in Xizang, but there are 458 recorded species of Protozoa, 208 Rotifera and 59 Crustacea, and the estimated potential fish biomass is 49.2 kg ha-1 (lakes 53.6, reservoirs 47.4, swamps 40.8: Anon., 1981).
Western China has a comparatively small fish fauna of 190 species, most of them members of the Central-Asian Plateau Complex (Li, 1981). There are many taxonomic works dating from the 19th century, including key papers by Günther (1859-70, 1876), Kessler (1876, 1879), Herzenstein (1888-91), Fang (1935, 1936), Li (1966, 1981), Chao et al. (1980) and Wu and Tan (1991).
A list of species is shown in Table 5. In Qinghai there are 66 species in 4 orders, 6 families and 31 genera (Wang and Jian, 1988). Only three of the 48 species native to Qinghai are fished commercially, whereas six of the 18 introduced species are utilized. In Xinjiang there are 90 species in 8 orders, 20 families and 55 genera (Liu et al., 1989); 50 species are native and 20 (8 native and 12 exotic species) are commercially important. In Xizang there are 56 species in 2 orders, 4 families and 21 genera, of which 10 species (all native) are economically valuable.
The fauna of the Qinghai-Xizang Plateau is broadly like that of Xinjiang, and includes 112 native and 17 introduced species (Wu and Tan, 1991). The native species are a relict of mass extinctions in the Quaternary, when uplift of the Himalayas transformed the prevailing low-altitude tropical or subtropical conditions to the present cold, arid, high-altitude climate (Wu, 1980; Chen, 1982; Wu and Tan, 1991). Several species of loach (Cobitidae: Nemacheilinae) are endemic to the plateau (Wu and Tan, 1991). Members of the subfamily Schizothoracinae (naked carp or "snow trout") are an evolutionary offshoot of the Cyprinidae. Some schizothoracines are endemic to the region. Their growth is slow (Hu, 1975) and their fecundity less than 10% of that of lowland species. Most adult individuals are scaleless or have only columns of scales around the anus (Zhu, 1981), although those from populations at lower altitudes may have a layer of fine scales. Of the Chinese species only Gymnocypris przewalskii, endemic to Qinghai Lake, has been studied in any detail. There is information on reproduction (Guong and Hu, 1975; Hu, 1975; Zhu, 1975), age and growth (Zhao, 1975), feeding (Wang, 1975), population dynamics (Zhang, 1984; Zhao, 1982) and the effects of water quality (Hu, 1975).
Some native regional species and varieties have been introduced to other parts of China. For example, the oriental bream (Abramis brama orientalis) and roach (Rutilus rutilus lacustris) have been introduced to many provinces (Liu et al.,1989), and the naked carp (G. p. przewalskii) has been translocated to Huangqi Lake in Inner Mongolia (Zhao et al., 1981; Qu and Guo, 1988).
3.1. Fish growth rates
Fish growth rates vary greatly in different parts of western China, depending on the food supply and physical and chemical features of the local aquatic environment. Growth curves for a number of regional fishery species are shown in Figure 2.
In Xinjiang, growth rates of introduced fish, especially filter-feeding species, generally are faster than those of native species. For example, at age 2+ the introduced silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) average 530-900 g (and may attain 1060-1450 g), whereas perch (Perca fluviatilis) and oriental bream average only 135 g and 114 g respectively (Liu et al., 1989). Blunt snout bream (Megalobrama amblycephala) attain an average weight four times that of oriental bream at age 2+. Grass carp (Ctenopharyngodon idella) average less than 500 g at age 2+, reflecting a sparse food supply (low macrophyte biomass). The growth rates of bottom-feeding species like crucian carp (Carassius auratus) and common carp (Cyprinus carpio) are limited also by crowding and inter-specific competition, and attain a comparatively low maximum of 560 g at age 2+ in eastern Xinjiang (Liu et al., 1989).
Most introduced cyprinids do not fare well in the cold climate. Although cyprinids in south-eastern China typically attain a marketable size in about 2 years, the same species take 3-4 years in western China (and especially on the Qinghai-Xizang Plateau). Rainbow trout (Oncorhynchus mykiss) may grow quickly, however, under conditions of cage culture: at Longyangxia Reservoir on the upper Yellow River, where summer water temperatures are 15-18°C, most 2+ fish weigh more than 1 kg (Edwards, 1992). Several other reservoirs in Qinghai provide similar conditions, but are not yet exploited for intensive culture. Few of the native species have commercial value, and the naked carp of Qinghai Lake, the mainstay of provincial fisheries, generally takes about 10 years to reach a marketable size of 500 g (Walker et al.,1996).
In Xizang native fish exhibit slow growth rates, comparable to those of native species in Qinghai (Ren et al., 1983). There are no records for introduced species.
4.1 Historical development
Although fisheries have been established in western China for more than 40 years, they contribute less than 0.2% of regional agricultural production (Wang, 1987; Liu et al., 1989), owing to small markets and poor economic conditions. The local people traditionally eat mutton and beef, and the Tibetans in particular are reluctant to eat fish because they have religious significance. Before 1958 aquaculture was non-existent and activities were confined to artisanal and part-time fishing using simple gear. Over the past three decades, however, immigrations of Han people from other parts of China have provided a strong stimulus for fishery development.
From 1958-70 large-scale fishing commenced in Qinghai Lake, Bosten Lake, Ulungur Lake and Yamdrok Lake (Li, 1959; Chen, 1962; Yue and Huan, 1964; Liao, 1965; Liu, 1985; Liu et al., 1989). Yields increased markedly, and in 1960 the Qinghai Lake naked carp fishery produced a record catch of more than 28,000 t (Wang, 1987; Walker et al., 1996). Catches later declined rapidly, following the pattern typical of newly-exploited fisheries. Extensive stockings of reservoirs with fingerlings were also commenced during this period. Since 1978 management and planning have become a normal part of fishery operations, and there has been a growing emphasis on aquaculture, particularly in Xinjiang.
4.2 Capture fisheries
Capture fisheries in a number of lakes and rivers have played a key role in the supply of local fish protein in the past four decades (Table 6).
4.2.1 Lake fisheries
The Qinghai-Xizang Plateau includes many lakes (Wang, 1987), most with only one or two commercial fish species. Some of the more saline lakes are mined for minerals (Yu, 1986), but few are exploited for fish due to problems of transportation and other economic and logistic constraints. The fishery in Qinghai Lake is most important, as it supplied regional markets with about 200,000 t from 1958-91, and generally has contributed more than 85% of annual aquatic production in Qinghai Province (Walker et al., 1996).
In the past 30 years, increased aridity and pressures associated with a growing human population, particularly diversions of water for irrigation and flow regulation for power generation, have had major impacts on the lake fisheries. These factors have contributed to falling water levels and increasing salinities in some lakes, and some have dried completely (e.g. Lopnur in Xinjiang: Wang, 1987). The three most valuable lake fisheries, at Qinghai Lake (Qinghai) and Bosten Lake and Ulungur Lake (Xinjiang), have all been affected. Brief descriptions of the former two are included in section 7.
Bosten Lake and Ulungur Lake are the principal lake fisheries in Xinjiang (Liu, 1989), with a combined production that peaked at 7100 t in 1971 and is currently about
4000 t. The average yield in the province has increased from 15 kg ha-1 in 1981 to 139.5 kg ha-1 in 1987. In 1987 68,600 ha were stocked with fish, including reservoirs (63.5% of total area), natural lakes (11%), ponds (6.4%) and swamps (17.9%), and total production was 14,050 t. Seventy percent of this figure came from aquaculture, including production from reservoirs (33%) and ponds and swamps (>60%).
In Ulungur Lake remedial measures have been implemented to offset the effects of a 4.2 m fall in water level between the 1960s and 1987 (Liu et al., 1989). The annual yield fell from an average 2700 t in 1961-70 to 1890 t in 1971-80 (maximum 4500 t in 1971) and
1857 t in 1980-87. In 1987 the local government constructed a canal to divert water from the Erqishi River, and by October 1988 the lake level had been restored and fishery production had recovered to 3128 t. Macrophytes were re-established around the lake shore, restoring about 1300 ha of former spawning habitat.
Gyaring and Ngoring are oligotrophic lakes on the upper Yellow River in Qinghai Province (altitude >4000 m above sea level). They are 20 km apart, but linked by the river and so have similar fish assemblages including Chuanchia labiosa, Diptychus pachycheilus, Gymnocypris eckloni, Platypharodon extremus and Schizopygopsis pylzovi (Schizothoracinae) and Triplophysa microps (syn. T. dorsonatus), T. scleropterus and T. siluroides (Noemacheilinae). The fishery opened in the 1960s and has persisted despite difficulties in transport and marketing. G. eckloni and P. extremus are dominant in Ngoring and Gyaring lakes, respectively, and supply about 1000 t annually. Individual G. eckloni typically weighs 0.5 kg, with a maximum of 4 kg, and P. extremus averages 0.65 kg, with a maximum of 1.25 kg (Zhu et al., 1984).
Yamdrok Lake, Xizang, is the largest lake on the northern slopes of the Himalayas and contains only one economic species, Gymnocypris waddelskii (Schizothoracinae). The fishery opened in 1961, when a farm was established on the north shore, and the annual yield variously has been 255 t (1961), 500-750 t (1962-65), 200 t (1981) to 45-500 t (1982-92). There is no provincial fishery authority, and the catch is transported to the capital, Lhasa, and sold at relatively low prices. Six kinds of gear are used: (1) large seine nets, 646 x 21 m, operated by pairs of boats (average 500-750 kg per haul, and up to 5750 kg), (2) small seine nets, 24 x 10.5 m, operated from a single boat (average 100-250 kg per haul), (3) gill nets, introduced in 1982 and involving about 20 connected nets 50 x 2 m (average 27 kg per net), (4) blocking of river channels in the spawning season, (5) large seine nets set under the ice and, rarely, (6) small trawls.
Many lakes in western China support populations of the brine shrimp Artemia salina (Anostraca). In Ebinur Lake, Xinjiang, where the salinity is about 100 g l-1 (Geographical Institute, 1978), the biomass of Artemia is about 7000 t (Zhen, 1990) and the potential yield is 2000 t a year. Gahai Lake in Qinghai (near Delingha, not that near Qinghai Lake) has an annual winter egg production of 100 t (Yang, unpublished). The principal market is as food for hatchery-produced fry.
4.2.2 River fisheries
Among hundreds of rivers in the region, five are important as fisheries (Yue and Huan, 1964; Wang, 1987; Liu et al., 1989; Table 6), with a combined annual catch of about 2000 t.
(1) The Yellow River supports two regional fisheries. A small fishery using wooden boats and floating nets exists near the headwaters in Qinghai; this is active from April-October, and the mean annual yield is about 17 t. The other exists along a 400-km reach near the border between Qinghai, Gansu and Sichuan provinces (Fig. 1). The most important species are Gymnocypris eckloni, Gymnodiptychus pachycheilus, Platypharodon extremus, Schizopygopsis pylzovi and Triplophysa siluroides, with P. extremus accounting for more than 80% of the total catch. The average annual fishery production from 1958-83 was about 100 t, or about 60% of total fisheries production in Gansu Province, but it has fallen to about 40 t over the last decade.
(2) The Erqishi River, with annual discharge of 10.8 km3 and length of 546 km, is the only river rising in western China that drains to the Arctic Ocean. Large quantities of organic material are imported to the river from its grassland catchment, providing food for a variety of species. Commercial fish include Acipenser spp. (sturgeons), Abramis brama orientalis (bream), Brachymystax lenok, Carassius auratus (crucian carp), Cyprinus carpio (common carp), Hucho taimen (huchen), Leuciscus leuciscus baicalensis (dace), Lota lota (burbot) and Rutilus rutilus lacustris (roach). The mean annual fishery catch is 300-500 t.
(3) The Yili (Ili) River has an annual discharge of 11.8 km3 and a length of 400 km in western China, before it enters Kazakhstan. The fishery annual production is about 300 t, sustained mainly by common carp, with contributions from bream, sturgeon, grass carp pikeperch and other species.
(4) The Tarim River is the longest river (2179 km) in inland China, and has an annual fish production of about 500 t. Jian (1989) reported 36 zooplankton genera from two major tributaries, the Kaxgar (Kashgar) and Yarkant rivers. Native fish species including Aspiorhynchus laticeps and Schizothorax biddulphi have gradually been replaced by introduced cyprinids, notably bighead carp, black carp, common carp, crucian carp, grass carp and silver carp.
(5) The Kaidu and Konqi rivers, part of the Bosten Lake drainage, have lengths of 661 km and 550 km and annual discharges of 3.34 and 1.250 km3, respectively. Both have many shallow riparian swamplands and minor channels, with extensive stands of macrophytes. In the Kaidu there is only one economic fish species (Gymnodiptychus dybowskii), whereas the Konqi supports small numbers of cyprinids including common carp, crucian carp, grass carp and silver carp. Annual production in each river is about 100 t (Zhou, 1989).
In Xizang (Tibet) the Yarlung Zangbo River (which becomes the Brahmaputra River in India) is the main fish producer. Ninety five percent of Xizang's fishery production (500 t) originates from the Yarlung Zangbo and its tributaries. River fisheries in the region generally are limited by the rugged topography. The upper reaches of the Lancang (Mekong in Viet Nam), Nu Jiang (Salween in Burma) and Yangtse, are virually unexploited because the steep-sided gorges make access extremely difficult.
4.3 Aquaculture
4.3.1 Development
Aquaculture has become established in western China only in the past 10 years (Figs 3-4). In Xinjiang aquaculture production was 6855 t in 1986 (Liu et al., 1989), surpassing natural catches for the first time, and 12,280 t in 1988. In Qinghai total aquaculture production in 1986 was 208 t, and by 1988 it had increased to 250 t (11% of total fishery production). Aquaculture is not significant in Xizang.
4.3.2 Extensive Aquaculture
So-called "extensive aquaculture" utilizes both natural lakes and reservoirs as habitats for stocking with a variety of species. Many dams and other regulating structures have been constructed throughout western China in recent decades, although most are designed to meet irrigation needs and aquaculture developments have been incidental. There are about 617 reservoirs with total area 74,100 ha and volume 25.1 km3 (Liu et al., 1989). Thirteen are large (> 100 x 106 m3), 89 are medium (10-100 x 106 m3) and 507 are small (< 10 x 106 m3, sensu Lu, 1986). Some contained native species (e.g. A. laticeps, S. biddulphi), but these had little economic value and have been displaced by introduced species.
Until 1958 there were capture fisheries, mostly for native species, in only a few reservoirs. Subsequently the fauna has changed markedly with introductions of bighead carp, black carp, common carp, crucian carp, grass carp, silver carp and blunt snout bream. Artificial (hormone-induced) spawning of most of these species was perfected in the 1960s, and large numbers of fingerlings are now produced for stocking. About 16% (61,000 ha) of the available water area (390,000 ha) is used for aquaculture (Fan, 1981; Wang, 1987).
Most of the suitable environments are in Xinjiang, where in 1986 there were 12 large, 85 medium and 382 small reservoirs (total 53,300 ha, 5.57 km3). The total yield from the province attained 1000 t in 1966 (having been interrupted for a decade by political instability), and rose to 1360, 3479 and 6000 t in 1978, 1982 and 1990, respectively (Fig. 3). One third of Xinjiang's total aquaculture production is from reservoir fisheries. One operational constraint is that the reservoirs undergo large seasonal changes in water level, particularly in summer. For example, in spring 1986 the storage in Xinjiang was 66% of total capacity (3.67 km3, Water Conservancy Department, 1988). Following irrigation in spring and summer the storages were down to 23% of capacity, but restored to 40% by floods in August and September.
Some natural lakes in Xinjiang are also utilized. In 1980, fingerlings of 16 species from the Erqishi River were released into Sayram Lake (Pan et al., 1989); three species
(A. laticeps, Hedinichthys yarkamtensis, S. biddulphi) became well-established and now dominate the catch. In Bosten Lake, perch now comprises about 80% of the catch, although its small size and carnivorous habit have contributed to a decrease in the total yield (section 6.2).
Aquaculture production in Qinghai has expanded considerably since it became commercially significant in about 1981, and in 1988 it provided about 11% of total provincial fishery production (Fig. 4). Small-scale trials began in the late 1960s, but only 2% of the available area (310 of 21,000 ha, in 22 reservoirs) has so far been exploited. By 1986, 6 million fingerlings had been released. The Bureau of Aquatic Products hatchery in Xining has produced about 0.5 million common carp fingerlings, but most others are imported from central or southern China. The largest of 137 reservoirs in the province is Longyangxia Reservoir, with a potential fish-rearing area of 20,000 ha, but presently exploited only for experiments with caged rainbow trout (see below). There are another six medium and 130 small reservoirs and 530 small canals.
In Keluke Lake, a natural lake near Delingha in Qinghai, fingerlings were first stocked in 1973, and a yield of 200 t was attained a few years later (Zhao et al., 1981; Wang, 1987). The lake now is a consistent producer of common carp (about 70% of the catch) plus crucian carp and grass carp.
4.3.3 Aquaculture
Aquaculture has expanded following recent economic reforms, and there are now about 5000 ha of ponds in Qinghai and Xinjiang provinces. Numerous hatcheries and fingerling farms have been established, especially below dams. In Xinjiang the total production of fingerlings is about 100 million, with a potential capacity of 500 million, and the province is able to supply most of regional demand for stocking. Fingerlings of common carp, grass carp, crucian carp and common bream are used extensively for stocking in Qinghai. Techniques used include cage culture, raceway culture, warm-flowing water culture and pen culture. ntil recently the peak yield was 75 kg m-2 (Liu 1989), but Edwards (1992) has reported 113 kg m-2 for rainbow trout in a pilot program of cage culture in Longyangxia Reservoir. In comparison, tilapia (Oreochromis mossambicus) cultured in the warm-water effluent from power stations may produce 30-90 kg m-2 (Liu et al., 1989). Trials have been conducted at Ürümqi, the capital of Xinjiang, and in Qinghai.
4.4 Fishery management stations
Although techniques for lake fishery management are scarcely developed, reservoir fishery management is comparatively sophisticated because a number of Fishery Management Stations (FMS) were established in the 1980s (Liu, 1983, 1984; Lu, 1986). These have imposed seasonal restrictions to protect valuable species, especially during spawning when fishing on river beds and at river mouths is banned, and certain kinds of gear are prohibited. The FMS annually stock fingerlings of various species in lakes and reservoirs, depending on the available food resources, and invest in fish escape-protection systems, fingerling culture ponds and other basic facilities. They also review annually the numbers of licences and quotas applying to licence holders.
4.5 Gear, processing and marketing
4.5.1 Fishing gear
Boats with large trawl or seine nets were introduced to the larger lake fisheries at the time when large-scale exploitation began, and the 125-hp wooden pair trawlers in Qinghai Lake were progressively replaced by 250-hp steel-hulled vessels in 1989 and 1990. In rivers, boats with outboard motors are used with gill-nets, trammel nets (especially in Xinjiang), seine and pull nets. Fixed nets are used in lakes of moderate or low productivity (e.g. Keluke Lake, Qinghai). During spawning runs in tributaries of the Yarlung Zangbo River in Xizang, parts of the channel may be blocked entirely and stop nets used to remove fish.
4.5.2 Processing and marketing
Most of the catch is transported fresh to nearby cities. In the 1960s, when production was high and prices low, frozen naked carp were exported to Lanzhou, Xian and other cities, but production since has declined considerably. Methods of temporary storage include salting, drying, freezing, gutting on ice, live fish (nearby markets only) and canning. The main marketing channels are the producers, including private, collective and state farms that sell directly to consumers in nearby towns, and companies that obtain fish from the producers to sell in local and distant markets.
4.6 Introduced species
Some 46 species, mostly cyprinids, have been introduced to the region from other parts of China since the 1950s. Several local endemic species have been translocated throughout the region and elsewhere, and some are now important fishery targets, having replaced native species. Methods for artificially-induced spawning have been perfected for many species. Introduced species of freshwater crabs, prawns and macrophytes have also become economically significant.
5.1 Qinghai Lake
5.1.1 Introduction
Qinghai Lake, the largest inland lake in China (Fig. 1), supports a fishery for an endemic species of naked carp, Gymnocypris przewalskii (Cyprinidae: Schizothoracinae). The species is unusual among cyprinids in that it migrates annually to spawn in rivers flowing to the lake. Its growth rate is slow as a consequence of the cold climate, and the fish generally take 7 years to attain sexual maturity and a marketable size of 300 g.
5.1.2 Environment
Qinghai Lake is at high altitude (3194 m) on the north-eastern margin of the Qinghai-Xizang Plateau, about 135 km from the city of Xining. It has a surface area of 4437 km2 and maximum depth of 26.9 m. The surrounding region supports more than 90,000 people, most of whom earn their livelihood from crops of barley and rape and herds of sheep, goats, yaks and other stock. The regional climate is typical of high-plateau semi-arid grasslands, with average monthly temperatures between -12.7°C in January (minimum -30°C) and 12.4°C in July (maximum 28°C). Ice covers the lake in November-March each year. Annual precipitation is about 386 mm and evaporation about 1460 mm. The lake has a dimictic circulation pattern despite being moderately shallow (mean depth 18.4 m) and exposed to strong northwesterly winds.
The basin has been endorheic since the Quaternary, when tectonic changes sealed its outlet to the Yellow River (Academia Sinica, 1979; Chen 1982, 1991) and isolated G. przewalskii from its original stock (cf. G. eckloni). Since then the lake has regressed to about one third of its original size and became saline (presently 12.5 g l-1). The water is strongly alkaline (pH 9.2) and predominantly sodium chloride, but with significant amounts of magnesium sulphate. Oxygen levels average about 4 mg l-1, and the bottom water generally remains oxygenated although hydrogen sulphide levels indicate some deoxygenation of the bottom sediments. Nutrient levels are about 0.02 mg P l-1 and 0.04 mg N l-1, indicating oligotrophy. A limnological survey of the lake in 1961-63 is described by Academia Sinica (1979).
The lake water level has fallen more than 12 m in the past century (1.85 m in 1961-90), mainly as a result of increasing aridity. The salinity increased from 12.5 g l-1 in 1961 to 14.5 g l-1 in 1989 (cf. Chen et al., 1990), but returned to 12.5 g l-1 in 1990-92. Recent experiments with naked carp fingerlings indicate an upper salinity tolerance (LD50) of 18.4 g l-1 (Walker et al.,1996), and suggest that survival of the fish population may be prejudiced if the lake salinity rises in future.
About 80% of the annual inflow to the lake is contributed by the Buha, Shaliu and Haergai rivers. Irrigation weirs constructed on the Shaliu and Haergai in the late 1950s have reduced the spawning grounds for naked carp, and only the Buha now provides unrestricted access. The Buha has begun to downcut its channel in response to the falling lake level, however, causing erosion and siltation that may also affect spawning.
5.1.3 Fauna and flora
Sixty six phytoplankton genera are recorded from the lake, including 23 Bacillariophyta, 26 Chlorophyta and 12 Cyanophyta, and dense growths of the chlorophyte Cladophora prevent trawling activities in some areas. The zooplankton comprises 57 taxa, including 9 Protozoa (mainly Carchesium), 21 Rotifera (Hexarthra fennica), 17 Cladocera (Moina rectirostris) and 10 Copepoda (Arctodiaptomus salinus). The benthic fauna includes 43 taxa, including an amphipod (Gammarus sp.), 34 insects, 5 molluscs and 3 oligochaetes, but chironomids (especially Tendipes reductus complex) comprise 87% of the biomass. Species of Potamogeton, Zannichellia qinghaiensis and other macrophytes occur sparsely in near-shore areas (Chen, 1987).
The naked carp G. p. przewalskii is the only commercial fish species present, although a subspecies, G. p. ganzihonensis, occurs in the Ganzi River, isolated from the main lake since the 1960s. Four species of the loach genus Triplophysa (Cobitidae: Noemacheilinae) occur in the rivers and near the lake margins, but little is known of their biology.
Seasonally, large bird populations are associated with rookeries at Bird Island, near the mouth of the Buha River. The lake attracts thousands of cormorants (Phalacrocorax carbo sinensis), gulls (Larus brunnicephalus, L. ichthyaetus) and other species that feed upon the fingerlings and fry of naked carp.
5.1.4 Fishery
History
There has been a fishery for spawning naked carp in the Buha and Shaliu rivers since at least the 19th century, when the fish were abundant and easily captured by a variety of simple methods. In 1958 the fishery was opened to commercial exploitation and trawling and gill-netting became the main methods of capture. In 1960 the forerunner of the present Bureau of Aquatic Products was established and a factory was built on the lake shore. In 1960-62, the boom years for the fishery, as many as 10 pairs of trawlers were active. From 1963-82 two pairs of boats supplied the factory and another supplied the region of Gangca. A Fishery Management Station was established in 1979, but its role appears to have been minor apart from drafting regulations (see below). From 1982-89 there were two pairs of 150-hp trawlers working for the factory, plus a third 120-hp pair serving the State Farm (near Gangca) in 1985-86. A pair of 250-hp steel trawlers was introduced in September 1989 and another in November 1990, and the older wooden boats were phased out.
Since the trawl fishery commenced catches have also been taken by other legal and illegal means. Licenses have been granted periodically for trawling (e.g. to support the State Farm) and for the use of gillnets. These catches have been subject to licenses and regulations, but without significant surveillance or enforcement. There has also been extensive illegal fishing, mainly using gillnets. There are no records of catches other than those landed at the Fish Factory.
Long-term yield
Trends in the yield of the fishery over the past 40 years or so are shown in Figure 4. These are official records, and take no account of illegal catches. After 1986 trends are affected by an annual factory quota of 1200 t (see below). It is unclear whether this quota has been rigorously applied, but it probably has served as a brake on fishing effort.
In general, the pattern is typical of newly-exploited fisheries, with high initial catches decreasing as the virgin stock of large, older individuals is removed. The catches peaked at 28,523 t in 1960 but declined to about 4000 t some five years later. Catches between 1965 and 1980 fluctuated between 3639-4979 t, but after 1980 there were indications of a slow decline (Fig. 4). Since 1986 an annual quota of 1200 t has applied to the factory trawlers. Other trawling permits were rescinded, and a system of licensed gillnets was introduced, with a nominal (but apparently un-enforced) quota of 800 t. The legal annual catch therefore is about 2000 t. The best-available estimate for the illegal catch is about 1000 t (Walker et al., 1996), suggesting a total annual catch of about 3000 t. Piscivorous birds are believed to capture another 700 t (Hu, 1975; Zhao, 1982).
Zhang and Chen (1980) used the Beverton-Holt Dynamic Pool Model and catch data available to 1976 to estimate the sustainable annual yield as 4791 t. This assumed an age of first capture of 10 years and a fishing mortality coefficient of 1.25. In fact annual yields of about 4200 t in 1975-77 were obtained with age of first capture 7.0 years and fishing mortality 0.50. Zhang and Chen suggested that if the age of first capture was raised to 10 years by increasing the trawl mesh size, the weight of the catch would increase by 10%, still short of the theoretical maximum. Alternatively, a larger catch could be obtained by an increase in fishing effort, but the necessary capital investment would offset the economic gain. Increased mesh size therefore appeared to be the best option for increased catches. In view of the apparent stability of the yield over 1975-77, however, they suggested that it was prudent to maintain the mesh size and so maintain the yield at the prevailing level.
This advice was followed only in part. In 1979 the codend mesh size of the factory trawl nets was increased from 6.5 to 7.5 cm (stretched mesh) and the mouths of the trawls were slightly reduced in depth. The most significant change has been the introduction of the more powerful steel-hulled trawlers after 1989. Whereas in 1980-89 the catch per unit effort (CPUE kg per hour trawled) from four trawlers operating in a zone near the factory was 400-500 kg per hour, the new trawlers have recorded values approaching 700 kg per hour. The steel trawlers appear to be able to fill the annual quota more quickly, and within a smaller distance from the factory, than their wooden counterparts. There is no doubt that the new trawlers are capable of a further increase in effort.
Changes in the fish stock
There is patchy evidence that the average sizes of fish in the commercial catch have declined since 1958. This is typical of the initial stages of fishery exploitation, and does not necessarily mean that the trawl fishery is causing long-term damage to the stock. More compelling evidence exists, however, to show that the present trawler catch does include many under-sized fish. As a general rule, fish smaller than 300 mm length and 350 g weight are likely to be less than 7 years old (these limits also correspond broadly to sexual maturity and a marketable size). In 1992, random samples of the commercial catch showed that significantly more than half of the catch consisted of individuals less than 7 years old, and that the effective age of first capture was about 5 years. The present fishery regime clearly is not sustainable in the long-term.
Present fishery regulations
Regulations were imposed by the local FMS at the time of its establishment, and have been reviewed periodically. In 1986 an annual quota of 2000 t was set, including 1200 t taken by the fish factory and 800 t taken by local residents using gillnets under license. The factory trawlers are permitted to exploit any grounds except reserved zones off the mouths of the two main spawning rivers, the Buha and Shaliu. The FMS annually issues some 400 licenses for local residents, using gillnets supplied by the Bureau of Aquatic Products. There is a minimum mesh size (80 mm), but no limit to the number of nets that may be used, and annual quotas of 1000 kg and 500 kg apply to full- and part-time fishermen, respectively. Gillnets are not permitted in the reserved zones, or in the rivers themselves, and their use generally is restricted in October and November and prohibited in winter.These regulations are not strongly enforced as there are few fishery officers in the area.
Handling, processing and marketing
When the pair trawlers are operating in the zone nearest the Fish Factory ("South Bay"), expeditions are completed within one day, beginning at about 7 am and ending in on return to the factory jetty in the late evening. Trips farther afield may extend over a few days. The boats generally complete three or more 2-hour trawls in one day, each alternately playing an active and passive role in laying and retrieving the nets. The trawl nets are emptied on deck and the fish are loosely crated and stacked on deck. On return to the jetty the fish are unloaded into an open truck, weighed at a weigh-bridge and transported to a processing room. The contents of the truck are offloaded on to the factory floor and handlers move in to pack the fish into 20-kg freezer trays. These are topped with water and frozen (-20°C); next morning the frozen blocks are glazed and transferred to a cool store pending transport to market.
In cool months (e.g. April), when the lack of refrigerated transport is not a problem, the freezing process may be circumvented and the catch may be transported to markets in Xining and sold fresh. Later in the season most of the catch is frozen and transported by road to Xining. Part is consigned to local markets, and part is air-freighted to Lanzhou (Gansu Province) and other regional centres. Blocks that thaw in transit are re-frozen.
Although naked carp are widely available in markets in Xining and other cities, they are not well-regarded by the local people. They generally command a low market price of RMB2-4 (in 1993) per kg for fresh fish, and less for frozen fish, whereas live common carp sell for about RMB10-15 per kg and fresh rainbow trout for up to RMB20 per kg (in 1993 US$1 was approximately RMB5). Consumers complain of many bones, especially in smaller fish, and the testes of male fish can cause digestive upsets if the fish are not cleaned before cooking. A significant part of the low market appeal, however, must stem from poor standards of processing and presentation. The frozen fish especially lack texture, and the practice of re-freezing thawed blocks must increase the risk of bacterial contamination and hence digestive upsets. Improved standards of handling, processing and presentation would surely increase the market value of the fishery products.
Prospects
The high level of recent investment in the fishery, particularly the four new trawlers (approximately US$100,000 each) plus new factory buildings and plant, is difficult to reconcile with the economic status of the fishery. The precarious situation relating to the high proportions of under-sized fish in the trawler catch shows that the net mesh should be increased (say, to 10 cm), and suggests that no increase in fishing effort should be permitted in the foreseeable future. The degradation of spawning areas caused by riverbank erosion and siltation, and the construction of impassable weirs on some rivers, also highlight the need for protective regulations. In fact regulations do exist "on paper", but the lack of adequate police enforcement means that these are widely disregarded.
Although it seems unlikely that the fishery will return a profit in the near future, given the scale of recent investments, there is scope for increasing the market value of naked carp products by better methods of marketing. It would be feasible, for example, to establish a pilot mincing plant, and even the value of frozen fish could be increased by improvements in hygiene and handling (Walker et al., 1996). Increased market value may be a disadvantage, however, for poorer people unable to afford higher prices, so that economic arguments will need to be weighed carefully against social and cultural factors. The major factor limiting development of the fishery is the lack of expertise in such critical areas as monitoring the lake environment and the performance of the fishery, policing the regulations, and handling, processing and marketing. Expertise will develop only if the provincial government makes a sustained commitment to management, with advice from authorities in China and other countries.
If the status quo is not challenged, it seems inevitable that the Qinghai Lake fishery will decline. If it does collapse, recovery of the fishery-and the lake ecosystem as a whole-may be extremely slow, retarded by the cold climate and the long generation time of the fish population.
Some consideration has been given to the introduction of other fish species to diversify the Qinghai Lake fishery. In the 1960s unsuccessful attempts were made to introduce two species of mullet (Mugil soiuy, M. sp.: e.g. Li, 1959), and it is possible that introduction of rainbow trout may be considered in future, if recent developments in aquaculture are supported (Edwards, 1992). The harsh environment militates against the survival of other species, however, and the fact that G. przewalskii is endemic to the lake also must argue against further introductions. The entire Qinghai Lake ecosystem would be irrevocably changed by introduced fish species.
5.2 Bosten Lake
5.2.1 Environment
Bosten Lake in Xinjiang (Fig. 1) has an area of 100,000 ha and a mean depth of 2.5 m (Table 1), and there are several nearby smaller lakes (total 3300 ha). The climate annually provides about 180 days with temperatures above 10°C, and so is favourable for the growth of cyprinids. Average air temperatures range from -15.5°C (minimum -30.4°C) in January to 24°C (maximum 39.2°C) in July. Average annual precipitation is 66 mm and evaporation is 1983 mm.
The fishery has been adversely affected by changes in the salinity and surface level of the lake. Since the 1950s irrigation projects have diverted water from the lake, and a 2-m fall in the surface level has reduced stands of littoral water plants and fish spawning areas. The salinity has increased from 0.39 (1958) to 1.84 g l-1 (1983) to the present 1.95 g l-1. Other environmental data are shown in Table 1.
5.2.2 Fauna and flora
Fifty four genera of phytoplankton are recorded from Bosten Lake, including the dominant diatoms Ceratium hirundinella, Chodatella sp. and Navicula sp. Typical phytoplankton cell densities are 25-67 l-1 (maximum recorded 1.280 million l-1). Aquatic plants (24 species in 16 families) cover 5-25% of the lake area, including stands of Phragmites communis and Typha sp. near the mouth of the inflowing Konqi River (Lu et al., 1979). Primary production is 1.64 g m-2 per day, indicating a potential fish biomass of about 99 kg ha-1 (Liu, 1989). There are 39 zooplankton genera, typically in densities of 1500-2000
l-1 (minimum 200, maximum 10,600 l-1). There are few data for benthos, but the snails Radix and Hippentis are common, and shells of Valvata are common in swamps associated with the inflowing rivers. Species of Chironomus and Nais are present.
The Bosten Lake complex originally supported four native species (Aspiorhynchus laticeps, Hedinichthys yarkametensis, Leuciscus leuciscus baicalensis and Schizothorax biddulphi), but others have been introduced and there are presently 24 resident species. A. laticeps has since disappeared and S. biddulphi is rarely seen.
5.2.3 Fishery
Prior to 1965 the catch in Bosten Lake was about 100 t annually, dominated by A. laticeps and S. biddulphi (Table 7). Fingerlings of bighead carp, black carp, silver carp, grass carp, common carp and crucian carp were introduced in 1962-65 and became major targets in 1972-78. In 1966 a fish farm was established to promote artificial spawning and culture of fingerlings for stocking, and in 1968-71 more than 2 million fingerlings of species from the Erqishi River were produced (e.g. Leuciscus leuciscus baicalensis, Rutilus rutilus, Tinca tinca and Perca fluviatilis). Artificial spawning of grass carp and silver carp has been particularly successful, and about 5.5 million fingerlings have been introduced to the lake since 1973. Since 1978 perch has dominated the catch (55-78%), and the total annual catch now is about 500 t.
From a fishery viewpoint, the lake possesses good water quality and abundant plankton, but it has sparse benthos. In addition, the proportion of carnivorous fish (perch) is considered too high. An FMS established in 1980 has imposed the following measures:
Fisheries in western China generally are limited by the lack of fishery traditions among the local people (hence a small market), although in recent decades the population has changed with immigration from provinces where these traditions are well-established. The remoteness of the region limits access to larger markets, however, and aquaculture is significantly more expensive than in lowland areas because feed must be imported. The paucity of native species is a further limitation, and although it has been partly offset by translocations of species from elsewhere, further introductions would present obvious dangers for the native fauna. The climatic trend towards increased aridity and the growing demand for irrigation water will also limit development, and fishery requirements will need to be carefully integrated with those of other consumers to minimise conflicts over water use. Perhaps the ultimate constraints are imposed by the cold, high-altitude climate, as cold waters have inherently lower productivities than warm waters, reflecting the shorter growing season. This tends to amplify the pressure on natural fish stocks and increases the likelihood of over-exploitation. The fate of both present and future fisheries will depend critically upon resource management.
Fisheries are most likely to develop further along transportation corridors and near major population centres, favouring selected species as a basis for capture fisheries and establishing key species in culture. Capture-fishery production probably has peaked in
Xinjiang (Liu et al., 1989), but there is potential for more development on the Qinghai-Xizang Plateau. Production could be stabilised, possibly at 10,000 t in each of the three provinces. This would depend upon management because the natural fish stocks are highly vulnerable to over-exploitation and recovery would be a very long process. Sustained yields will require careful determination, administration and policing of catch quotas, and no less careful attention to factors affecting recruitment.
Aquaculture has potential for expansion, particularly in Xinjiang where production has been growing at an annual rate of about 30% (Liu et al., 1989), although this will require investments of foreign capital. There presently are few hatchery and food-production facilities near reservoirs, causing shortages of fingerlings for stocking, especially in the more remote areas (Lu, 1986). If these obstacles are overcome, there are likely to be fundamental changes in the structure of the regional fisheries. Aquaculture is likely to be most strongly supported, as it enables a comparatively high yield. Promising recent trials with caged rainbow trout in Qinghai, noted earlier, may provide a basis for expansion in the near future. Ideally, development should be guided by establishing fishery research centres responsible for basic research, collection of fishery statistics, selective breeding and stocking. This would encourage a higher level of sophistication in fishery management than now prevails.
The authors are grateful to Dr. Ian Dunn and Dr. David Edwards for comments on early drafts, and to Professor Wu Yunfei, Senior Engineer Chen Yuan and Professor Yu Shongshen for information and advice.
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