FISH STOCKS AND FISHERIES IN IRRIGATION SYSTEMS IN ARID ASIA

by
T. Petr
27 McLeod Street, Toowoomba, Qld 4350, Australia

Abstract

The arid zone of Asia extends from the Mediterranean to the Pacific, including the following countries: Turkey, the Syrian Arab Republic, Iraq, Iran, the Russian Federation, Afghanistan, Mongolia, Pakistan, India, China, and countries of Central Asia, i.e. Turkmenistan, Uzbekistan, Kazakhstan, Kyrgyzstan and Tajikistan. In all of them most food crops are produced using irrigated agriculture. In Central Asia, including southern Kazakhstan, over 80 percent of the total water use is for irrigated agriculture. In Pakistan 78 percent of the arable land depends on irrigation as compared with 100 percent in Egypt, 33 percent in all Asia, 21 percent in Near East and Africa, 8.5 percent in Latin America and 2.7 percent in sub-Saharan Africa. In Central Asia, at the end of the 1980s there were over 40 large reservoirs already constructed, with their primary purpose being storage of water for irrigation, closely followed, in some cases, by hydropower production. Fisheries managers have had a number of options for fishery development in the irrigation systems, including reservoirs, major irrigation and drainage canals, and waterbodies established from residual irrigation water. Most options have been a response to the impacts caused by the manipulation of water resource for purposes other than fisheries. Stocks have been enhanced by introductions of species with known preference for such waterbodies and by regular stocking of seed produced in hatcheries. In slow flowing large canals and side storage reservoirs, such as those alongside the Karakum canal in Turkmenistan, fish with pelagic eggs, such as Aral barbel, razor fish, the introduced Chinese carps and white Amur bream (Parabramis pekinensis) have been doing well. Some of the drainage collecting depressions have been utilized; the Aral Sea catchment has 2 341 of these depressions, covering 7 066 km² surface area. However, they are characterized by elevated salinities and high concentrations of agrochemicals, the latter being a major obstacle for using fish for human consumption. The fisheries management in waterbodies of irrigation systems of the arid countries in Central Asia has been facing not only major environmental problems, but also those arising from the transition to market economy. Co-management and community-based management of irrigation waterbodies is being considered among the options which could be applied under the new privatization policy. However, in the newly independent countries of Central Asia, the major problem is now lack of funds for urgently needed rehabilitation of some of the existing structures, as well as for the development of small-scale fish enterprises as an alternative to the still prevailing large fish production and fishery systems inherited from the Soviet era, which can no longer be maintained.

1. Introduction

In developing countries approximately 80 percent of water used is for irrigation. It is estimated that in the year 2010, 45 percent of the total global food production will come from irrigated lands. To develop irrigation on such a large scale, many engineering works are needed. At the beginning of the 1990s there were over 36 000 dams in the world (Pircher, 1993), with many of the resulting storages serving irrigation. Some rivers now have a cascade of reservoirs, with little or no free flowing water in between them. Irrigation systems, which consist of dams storing water in reservoirs, of main irrigation canals and their distributory net, drainage canals, and often drainage water storages, offer a diversity of waterbodies for fish production. On the other hand, such systems exercise a negative impact on fish stocks of the original riverine habitats, which are no longer available to them. The impact of damming rivers on fish stocks is well-known: in reservoirs the number of riverine fish species diminishes and they are replaced by fish species with a preference for standing waters, subject to their presence in the catchment. The period of water permanency in irrigation canals is often a limiting factor on their use by fish. Residual waterbodies have a high evaporation rate under desert and semi-desert conditions, and fish face elevated salinity levels, as well as high concentrations of agrochemicals which may be used in irrigated crop production. While all this represents formidable obstacles for the fish, careful management of some irrigation waterbodies is capable of replacing the losses in fish production due to damming rivers. It is the objective of the Expert Consultation to discuss the fishery management practices, constraints imposed on them by irrigation, and what can be done in the region for enhancing fisheries in irrigation systems.

2. Situation in the arid zone of Asia

The arid zone of Asia extends from the Mediterranean to the Pacific, including the following countries: Turkey, the Syrian Arab Republic, Iraq, Iran, the Russian Federation, Afghanistan, countries of Central Asia, i.e. Turkmenistan, Uzbekistan, Kazakhstan, Kyrgyzstan and Tajikistan, Mongolia, Pakistan, India and China. In all of them most food crops are produced using irrigated agriculture. All countries in the arid zone tap their inland water resources for irrigated agriculture, and many of the waterbodies have harvestable fish stocks. In Central Asia, over 80 percent of the total water use is for irrigated agriculture. In Pakistan 78 percent of the arable land depends on irrigation as compared with 100 percent in Egypt, 33 percent in all Asia, 21 percent in Near East and Africa, 8.5 percent in Latin America and 2.7 percent in sub-Saharan Africa. In 1987, in 93 developing countries of the world, a total of 164.7 million ha of land was irrigated. This was expected to increase to 220 million ha by year 2000 (FAO, 1993). The irrigation demand ranges from the extreme of the total diversion of water of some rivers for irrigation, to partial diversions and use, with the consequence of various degrees of flow diminution downstream of water abstraction.

In Central Asia, at the end of the 1980s there were over 40 reservoirs constructed or under construction (Nikolaenko, 1988). In the basin of the Syr-Darya Salikhov and Kamilov (1995) counted 22 reservoirs, covering a total of 1 854 km², and 17 reservoirs (1 463 km²) in the basin of the Amu-Darya. In Uzbekistan all four major rivers, Syr-Darya, Zarafshan, Kashka-Darya and Amu-Darya, and their tributaries have been regulated and have storages for irrigation (Kamilov and Urchinov, 1995). Their major purpose is to keep sufficient amount of water of required quality for irrigation use. An example of the increasing demand for irrigation water in Turkmenistan was given by Kostyukovsky (1992): while in 1900, with a total population of 1 444 000, there were 5 530 km² of irrigated land, requiring 3.68 km³ of water, by 1986 (population 5 446 000) this rose to 17 830 km², which required 16.50 km³ of water. Micklin (1991) produced a map of the major irrigation zones in Kazakhstan and Central Asia (Fig. 1).

Fig. 1 Major irrigated areas in Central Asia and Kazakhstan (Micklin, 1991)
1. Turkmenistan; 2. Karakalpakstan; 3. Uzbekistan; 4. Kazakhstan; 5. Kyrgyzstan; 6. Tajikistan

Under arid conditions of Central Asia the average evaporation rate is two-fold that of precipitation. This leads to salinization of water and soils. The long-term average salinities of reservoirs in the montane and foothill zone above 500 m altitude range from 223 to 527 mg/litre, with maximum salinities reached during winter and spring, before floods. In lowland reservoirs the salt concentration ranges from 550 to 1 200 mg/litre, with a maximum of 1 700 mg/litre reached during the autumn-winter period (Nikolaenko, 1988). Nikolaenko (op.cit.) also compiled information on average salinities of 13 reservoirs of Central Asia (Table 1). It shows that by the mid-1980s in four out of 13 reservoirs salinities exceeded the value of 1 g/litre. Water quality in the reservoirs of Central Asia started deteriorating in 1974 when drainage waters, with a high concentration of sulphates, chlorides, manganese and sodium, were diverted back into rivers.

Table 1
Mean salinity values (mg/litre) for 13 reservoirs situated in Central Asia.
(from Nikolaenko, 1988)

The quality of water available to agriculture is as important as the quantity. Depending on the crop, crop production decreases with increasing salt concentration in water and soil. The same applies to freshwater fish. Salinization of surface waters resulting from reintroduction of drainage and wash water from irrigated fields is a common problem in arid and semiarid zones. While water with salinity over 1 mg/litre is considered unsuitable for the usual crops, less is known about water salinity levels harmful to especially the young of the native fish of arid and semiarid climates. Agricultural practices also affect nutrient concentrations in surface and groundwaters. In surface waters, this may result in a ready availability of nutrients to aquatic plants, leading to excessive growth of plants in irrigation and drainage canals. Antagonistic interactions between the agriculture and fisheries sectors arise from the application of pesticides and herbicides which can be harmful to aquatic living organisms. Agrochemicals used against pests or for defoliation, such as in cotton production, contribute to serious water quality problems and represent a hazard to fish and the end consumers - birds and man. Where drainage and wash waters are diverted in desert depressions without an outflow, such as Lake Sarykamysh in Uzbekistan, or into swamps, agrochemical concentrations may gradually reach unacceptable levels making the fish unsuitable for human consumption.

3. Fish stocks and fisheries in irrigation systems of the arid zone of Asia

Irrigation systems require a novel approach to fishery management. Where large reservoirs have formed, riverine fish may not find the new habitat suitable for all periods of their life cycle, and their number will gradually decline, with some species disappearing completely. While a new management approach is required, some of the knowledge on reservoir fish and fisheries can be adapted from similar situations where a river was dammed for hydropower electricity production. Indeed, reservoir fisheries in some parts of arid Asia have been well advanced, for example in some countries of Central Asia and in India. Stocks have been enhanced by introductions of species with known preference for such waterbodies. Elsewhere, or in addition to introductions, reservoirs have been regularly stocked with fingerlings produced in hatcheries. This has resulted in a sustainable production of fish from reservoirs such as Chashma in Pakistan and Kapshagay in Kazakhstan. Irrigation and hydropower reservoirs often experience a large and untimely drawdown which prevents the desired fish species from finding suitable spawning grounds. The inherent productivity of the reservoir is also important, with reservoirs with a large throughflow rate usually poor in fish food such as phyto- and zooplankton. Introductions and regular stocking of exotic fish, while increasing fish production, may lead to a change in fish species composition. Often the usually highly adaptable introduced species gradually replace the indigenous fish. While there may be a decline in indigenous fish species, introductions usually result in an increase in species diversity. But not always the final result is a substantial gain in fish production as known for the Kapshagay reservoir in Kazakhstan, where to maintain fish stocks for sustainable fisheries it is necessary to regularly stock this reservoir. As introductions may not result in a permanent establishment of all of the introduced species, to prevent a decline in fish catches fisheries managers may also pursue the strategy of bringing in additional exotic fish species to sustain the fish production and fishery. Eventually, such reservoirs may become inhabited largely by the exotics.

By blocking the migratory path of fish, dams have a major impact on fish species which require suitable spawning and/or nursery and feeding grounds. Dams on the Amu-Darya and Syr-Darya have blocked the migratory path of fish, such as Aral barbel (Barbus brachycephalus), shovelnose (Pseudoscaphirhynchus kaufmanni), sturgeon (Acipenser nudiventris), Aral trout (Salmo trutta aralensis), and pike asp (Aspiolucius esocinus) now threatened with extinction (Pavlovskaya, 1995). In 1974 a fishway opened on the Takhiatash dam on the Amu-Darya, about 200 km upstream from the Aral Sea, enabling a small scale upstream migration. Dams on the lower Indus and the Ganges have stopped the migration of hilsa (Hilsa spp). The large consumptive irrigation use of water from the Amu-Darya and Syr-Darya has impacted not only the fish stocks and fisheries in the terminal Aral Sea, but it also led to a decline in fish stocks and fisheries in the deltas of these rivers. (See also paper by Kamilov, this volume.) In northwestern China the total diversion of water for irrigation from several rivers has resulted in the disappearance of fish and fisheries. Stocks of the slow growing naked carp (Gymnocypris przewalskii) in the saline Lake Qinghai in the Qinghai Province of China have been hard hit by the combined impact of overfishing, blockage of the inflowing rivers by weirs preventing their upstream migration into rivers for spawning, and water diversion for irrigation (Walker and Yang, 1999).

Damming of the Ili River in Kazakhstan has had a negative impact on fish stocks and fisheries of the terminal Lake Balkhash. Retention of water in the Kapshagay reservoir on the Ili, and its partial diversion for irrigation, led to an increase in the salinity of Lake Balkhash and a consequent decline in fish landings (Petr and Mitrofanov, 1998). The desiccation of wetlands and lakes in the Ili delta resulted in shortages of food and spawning areas for carp and pikeperch, both fish known for their tolerance of waters with elevated salinities. The instability in the Ili River discharges, while caused largely by the highly variable rainfall over the years, has made the future of fish stocks in Lake Balkhash difficult to predict. No doubt, the presence of the Kapshagay dam has further contributed to the problems faced by fisheries. Much has been written about the impact of water diversion for irrigation from the Syr-Darya and Amu-Darya rivers on the fate of the Aral Sea.

4. Rehabilitation and enhancement of fish stocks and fisheries

Fisheries managers have a number of options for fishery development in the irrigation systems. Most options are a response to the impacts caused by the manipulation of water resource for purposes other than fisheries. As it is difficult to predict the weather pattern for each year, irrigation systems are subject not only to rainfall, but in some places also ambient air temperature, which determines the amount of snow- and ice-melt from glaciers, and evaporation rates. Agriculture practices such as selection of crops are also not static, and may change from year to year, and with them the amount of water and timing of the demand required for achieving the best crop. Furthermore, there is the use of agrochemicals, which may differ from year to year. Thus, fisheries managers, while having an overall master plan, may also need contingency plans, as fisheries in irrigation systems are subordinated to other demands for water. In addition, the fishery sector is usually underfunded by the government. The positive aspect of the former centrally planned economies of some countries in the Region was that they had a well-organized research and collection of statistics obtained through regular monitoring of fish stocks, so that the impacts of introductions, stocking, and catches could be evaluated and management strategies adjusted. Centralized statistics provided the longest series of data for a number of irrigation reservoirs situated in Central Asia, and these can now be used for further assessment, evaluation and as examples of the level of efficiency of the applied enhancement measures. They also show the failures resulting from some introductions. The following section provides information on four reservoirs in Central Asia and Kazakhstan, for which long series of data are available. Much of this information is abstracted from Karpova, Petr and Isaev, 1996.

4.1 Reservoirs

Chardara reservoir (formerly called Chardarin) is situated at an altitude of 252 m on the Syr-Darya in Kazakhstan, at its border with Uzbekistan. It is an example of the multiple-purpose of many similar reservoirs, in this case hydropower production, storage of irrigation water, municipal and industrial water supply, and fisheries. Unlike reservoirs in the temperate zone of Europe, the USA and Canada, it fills during autumn and winter. From the end of April/beginning of May to September/October the reservoir water is drawn for irrigation, with water level declining by up to 12 m. At the maximum drawdown the reservoir covers only 11 000 ha, as compared to 90 000 ha when full. There are 32 fish species in this reservoir, of which 14 are of economic importance. While initially bream (Abramis brama), the wild form of common carp ("sazan", Cyprinus carpio), pikeperch (Stizostedion lucioperca) and rasorfish (Pelecus cultratus) dominated in fish catches, the introduced and stocked common ("European") carp (Cyprinus carpio), which appeared for the first time in catches in 1987, reached 67 percent of the total catch in 1991 (Fig. 2). While the mean annual catch for the 12-year period 1980-1991 was 1 712 tonnes, equal to a yield of 19.0 kg/ha (as for the area of the full reservoir), in 1990 the catch was 2 565.9 tonnes, equal to a yield of 28.5 kg/ha. This was the result of the rapid establishment of the introduced common carp. Other fish species continued to appear in fish landings at approximately the same numbers as prior to the appearance of the common carp, thus indicating that its introduction did not negatively affected them. During the 1990s the reservoir fishery underwent major changes. For details see Ismukhanov and Mukhamedzhanov (this volume).

Fig. 2 Composition of fish catches in Chardara reservoir (Karpova, Petr and Isaev, 1996)

Kairakkum reservoir on the Syr-Darya in Tajikistan is situated at an altitude of 347.5 m, covers 81 300 ha when full, and 26 000 ha at the minimum operating level. It is providing water for irrigation, municipal and industrial demands, and it also has fisheries. During summer the water level in the reservoir sharply declines because much of the water is used for irrigation. This has a negative impact on fish stocks, especially during dry years. The reservoir fish species are the indigenous fish of the Syr-Darya. Bream, pikeperch, and wild carp dominate in fish catches, asp (Aspius aspius), wels (Silurus glanis), Aral white-eyed bream (Abramis sapa) and rasorfish are also species of fishery importance (Fig. 3). The introduced Chinese carps (grass, silver and bighead), which appeared in catches from 1988 onwards, made a minimal contribution to fish landings. The reservoir is not productive, with a mean annual catch of 481.2 tonnes for a 12-year period (1980-1991), which equals to a yield of 4.33 kg/ha. The yield could be perhaps doubled or tripled with sustained stocking, if there were to be a sufficient food base for the stocked fish.

The establishment of fish fauna in Kapshagay reservoir on the Ili River in Kazakhstan has been thoroughly studied by Mitrofanov et al. (1988, 1992). The Ili River enters Kazakhstan from China, and downstream of Kapshagay reservoir it ends in the slightly saline endorheic Lake Balkhash (Fig. 4). Kapchagay reservoir covers 184 700 ha when full, which happened for the first time in 1988, since the dam closure in 1969. The reservoir is multipurpose and serves hydroelectricity production, irrigation, transport, as a municipal and industrial water supply, for regulation of water discharges to maintain water quality downstream including in the major canals, and for nature conservation, recreation, and fisheries. Before the closure of the dam, 30 fish species were listed for the river (Petr, 1992). In 1975, 24 fish species were recorded in the reservoir, and only 19 species in the Ili River (Petr and Mitrofanov, 1998). Subsequently the number of fish species in the reservoir declined to 18 species by 1980. Commercial fishery started in 1972, and during the first years following the filling several fish species of economic importance were introduced, such as pikeperch, asp (Aspius aspius) and wels from the Ural River, Chondrostoma nasus and Leuciscus lindbergi from Lake Beilikol, and five species (Pseudorasbora parva, Pseudaspius leucocephalus, Hemiculter leucisculus, Percottus glehni and Rhinogobius similis) from the Soghua River in Heilongjiang Province in China. The initially dominant common carp was replaced by pikeperch, and this, in turn, by bream. With the water level now being subject to hydropower production and irrigation demands, and not seasons anymore, spawning opportunities for the common carp and some other fish have been greatly reduced. The manipulation of water level has not affected the breeding of bream which has pelagic eggs. Stocks of roach (Rutilus rutilus), crucian carp (Carassius carassius) and wels have also gradually built up and gained in fisheries importance. Spiny sturgeon (Acipenser nudiventris), never common in the river, virtually disappeared. In 1980 the catches were highly dominated by bream, with much less common wels, asp, wild form of the common carp and other species (Fig. 5). During the period 1980-1991 the mean annual fish landings were 1 008.6 tonnes, which equals to a yield of 10.1 kg/ha as per 100 000 ha, which is an estimate of the average maximum water level surface area during the observation period.

Fig. 3 Composition of fish catches in Kairakkum reservoir (Karpova, Petr and Isaev, 1996)

Fig. 4 Lake Balkhash Basin, Chu River basin, Lake Issyk-Kul (from Petr and Mitrofanov, 1998)

Fig. 5 Composition of fish catches in Kapshagay reservoir (Karpova, Petr and Isaev, 1996)

Toktogul reservoir in Kyrgyzstan is situated on the Naryn River, in the watershed of the Syr-Darya, at an altitude of 900 m. At a maximum water level it covers 28 400 ha, which is reduced to 15 000 ha at the minimum live storage. The reservoir serves for hydropower production and irrigation. The fish are those of the Naryn River and its tributaries plus a number of introduced species. Initially, in catches dominated the indigenous snow trout (Schizothorax intermedius), closely followed by the Amu-Darya trout (Salmo trutta oxianus) (Fig. 6). Commercial fishing started in 1978, but there were large differences between annual catches. A certain stabilization was noticed since 1988, when catches reached up to 25 tonnes/year, with the snow trout being the dominant fish in landings. The introduced silver carp (Hypophthalmichthys molitrix) and common carp were also a regular, but small component in the catches. More recently the introduced Issyk-Kul (Sevan) trout (Salmo ischchan gegarkuni) became an important commercial fish species. For additional information on this reservoir see Djancharov (this volume).

Fig. 6 Composition of fish catches in Toktogul reservoir (Karpova, Petr and Isaev, 1996)

Kamilov and Urchinov (1995) who compared the fish catches from 12 Uzbekistan reservoirs, found that Tudakul reservoir (17 400 ha when full) was having the highest yield of 30.9 kg/ha (547 tonnes for the whole reservoir), and a mean annual harvest of 453.5 tonnes (for the period 1987-1992). The potential sustainable yield was estimated to be around 78 kg/ha, if regularly stocked with silver, grass and common carps.

Fishery management measures in Uzbekistan reservoirs have included the introduction of several fish species plus their food organisms, and stocking. The results have differed among the reservoirs but usually with the increasing age of the reservoir species diversity has increased, as a result of introductions and of the immigration of fish from rivers and through canals. Fisheries, initially harvesting stocks which formed without human interference, are now paying more attention to the sustainability of stocks. Long-term research on several reservoirs has indicated that the major reasons for the low fish production in some reservoirs are: poor utilization of the natural fish food, poor spawning conditions and nursery habitats, and vacant niches not yet occupied by economically important fish species. In some reservoirs aquatic plants are underutilized, or benthos is utilized by fish species of low value. Fishery management programmes were prepared in the past for the major river systems of Uzbekistan which should lead to increasing fish yields four to six times, but implementation of the programmes has been delayed by the major political and economic changes, which have taken place in the country over the last 10 years. For more details see Kamilov (this volume).

4.2 Irrigation canals

The rate of water flow in the major irrigation canals usually ranges from 40 to 300 m³ per second, with a water velocity between 0.4 to 2.0 m per second. In some major canals, when not in use, a minimum flow of 5 m³ may be maintained. Where rivers carry a high sediment load, a sedimentation reservoir may be constructed at the head of the canal. While the average concentration of suspended sediments at the intake of water from the Amu-Darya into Karakum canal is 3.7 g/litre corresponding to a transparency of less than 40 cm, after the water leaves the sedimentation reservoir its transparency is much higher. But as the distance from the reservoir increases, the transparency gets gradually reduced due to the erosion of the canal sides. Apart from current velocity and water transparency, water salinity is also important for fish. In the Amu-Darya irrigation canals salinity ranges from 118 to 1 304 mg/litre (Ergashev, 1989), increasing towards the canal tail reach and final distributaries.

In slow flowing large canals and side storage reservoirs, as present alongside the Karakum canal in Turkmenistan, fish with pelagic eggs, such as Aral barbel, razor fish, the introduced Chinese carps and white Amur bream (Parabramis pekinensis) have been doing well. The introduced fish are well established in the Karakum canal and breed there. In a number of irrigation canals grass carp has greatly assisted in controlling aquatic plants. In the Karakum canal, the efficiency of this fish but especially its feeding selectivity has lead to a succession in macrophytes from Myriophyllum spicatum to Ranunculus, which is considered toxic to grass carp. Total removal of aquatic plants by grazers such as grass carp does not favour some other fish such as common carp, which needs aquatic plants for attachment of eggs, if it is to coexist with grass carp. Grass carp is also known to contribute to the eutrophication of those irrigation canals with dual purpose, i.e. irrigation and as a source of drinking water. Its use for control of aquatic macrophytes therefore has to be carefully planned, especially in desert, where other sources of water are not available. The eutrophicating impact of grass carp can be counteracted by the introduction of silver carp and bighead carp, which will feed on phytoplankton and this may prevent eutrophication of the canal water.

4.3 Lakes established from drainage waters

Where drains collecting residual irrigation water and wash water do not re-enter a river and/or a terminal lake, as required when the salinity of the drainage water exceeds 1 mg/litre, the water may be diverted to a depression, where it creates a new water body. Pavlovskaya (1995) estimated the number of drainage collecting depressions in the Aral Sea catchment at 2 341, covering 7 066 km² surface area. More than one third of drainage water collecting depressions and waterbodies are in the Syr-Darya River basin, where the largest is the Arsanay Lake system (4 000 km²). Twenty-four per cent of such waterbodies, with a total area of 52 percent of the total, are concentrated in the Amu-Darya River basin, with the largest, Lake Sarykamysh, exceeding over 3 000 km² in Uzbekistan and Turkmenistan. Kamilov and Urchinov (1995) and Pavlovskaya (1995) provided figures for fish catches for five drainage lakes. In 1992 fish landings from the Arnasay system, which had at that time a water salinity of 10.1 g/litre, were 1 141.4 tonnes. This was less than 40 percent of the maximum of 2 558.4 tonnes harvested in 1990. Only 334.5 tonnes were harvested in 1992 from Lake Sarykamysh, where water salinity has been gradually increasing and by 1992 reached 12.5 g/litre. Five years earlier fishermen harvested from the same lake 1 347.9 tonnes. In 1992, fish landings from three other lakes, established from drainage waters, were: 117.2 tonnes (Dengizkul), 5.3 tonnes (Karakyr), and 4.1 tonnes (Tuzgan). The best information on the impact on fish stocks and fisheries of the changes in the size and chemical character of a water body, established from drainage waters, is that available for Lake Sarykamysh.

Lake Sarykamysh

In Sarykamysh fishery started in 1966, with the major fishery organization located in Turkmenistan. In 22 years of commercial exploitation a total of 21 300 tonnes of fish were harvested. The maximum annual catch of 2 500 tonnes was recorded during the 1981-85 period, with yields ranging from 4 to 8 kg/ha. There was no restriction on fishing and the fishery resource was exploited to its maximum. Uzbek (Karakalpak) fishermen started fishing only in 1980, and stopped in 1988 as fishing became unprofitable due to the large distance between the water body and fish processing plant, and also because of the poor quality of fish (Pavlovskaya, 1995). The Karakalpak fishery area is situated in the north of this lake where the salinity is higher than that in the south. The high salinity prevents fish, such as common carp, Aral barbel and wels, from growing larger. The fishery focused on Aral barbel and common carp and due to the lack of enforcement of regulatory measures the stocks of these two species became overexploited. This was accompanied by an increase in the less valuable pikeperch and razorfish. However, the major problem has been the continuing increase in the lake salinity, which by 1995 was expected to reach 16-18 g/litre.

The Lake Sarykamysh experience has provided a number of lessons on the impact of a rapidly changing aquatic environment on indigenous and introduced fish and their fisheries. Sarykamysh shows the instability of lakes established from drainage water from irrigated agriculture in desert conditions with a high evaporation rate. Instability of especially the limnological environment is inherent in such lakes, which are subject to a gradual increase in salinity. Freshwater fish are stressed as the salinity affects the fertilization and hatching of eggs and retards growth of fish. Studies have shown that the ratio of predatory to prey fish increases, largely due to the increase in the number of pikeperch, which is the most salinity-resistant commercial fish species in the Aral Sea catchment. In Sarykamysh bream, pikeperch and razorfish were the most adaptable and productive fish under the increasing water salinity. Eventually, pikeperch represented 27 percent of the total fish stocks (Sanin and Shaporenko, 1991) but this was followed by their decline (Fig. 7).

The experience with Sarykamysh has shown that waterbodies with increasing salinity need a dynamic environmental and fishery management approach if they are to continue serving fish production. The deteriorating spawning conditions resulting from the increasing salinity may perhaps be compensated by breeding fish in hatcheries and stocking fingerlings. Other species, such as of estuarine character which tolerate large water salinity differences, could be also tested. A major problem is the increasing load of pesticides and other toxic substances applied in agriculture. Alternative solutions should be found for lowering agrochemical application levels and biological control should be introduced where possible (Petr and Mitrofanov, 1998). A certain decrease in the use of agrochemicals has taken place since countries of the Central Asia entered the transition period from centrally planned economy to market-oriented economy.

5. Discussion

Interesting information arises from a comparison of the fisheries in the pre-irrigation period in the Chu River catchment (Kyrgyzstan/Kazakhstan) with that of intensive irrigation. During the first period, i.e. in the 1930s, the catches in the River Chu were estimated at 4-5 tonnes in the submontane zone and 500-600 tonnes in the lowland lakes. By the 1960s, the annual catches in the lakes declined to 250 tonnes and in 1970 to as little as 20 tonnes. When comparing these figures with the volume of water uptake for irrigation, a direct relationship between the diminishing water discharge in the river and fish catch becomes evident. The poor fish catches in 1970 were when there was a maximum uptake of the river water (166 m³ s^-1) for irrigation. Between 1930 and 1970, the area of irrigated land doubled from 190 000 to 383 000 ha. By 1970, the total surface area of reservoirs in the montane zone reached 40 km². Pond fish culture expanded in the submontane zone and commercial fishing developed in Tashutkul reservoir. In 1971, the fish farms produced about 450 tonnes of fish for markets, but afterwards emphasis shifted to the production of stocking material for reservoirs. As a result, in the early 1980s the output of market fish was at the same level as in 1971 and the output of juveniles for stocking was 65 million per year. One can conclude that the total fish output in the watershed of the River Chu has remained the same as it was before the introduction of irrigated farming. However, the cost of producing the same amount of fish became much higher (Petr and Mitrofanov, 1998).

Fig. 7 The dynamics of the major fish species in catches from Lake Sarykamysh (1965-92). 1. Esox lucius; 2. Chalcalburnus chalcoides aralensis; 3. Hypophthalmichthys molitrix; 4. Rutilus rutilus aralensis; 5. Silurus glanis; 6. Aspius aspius iblioides; 7. Cyprinus carpio; 8. Barbus brachycephalus; 9. Abramis brama orientalis; 10. Stizostedion lucioperca; 11. Pelecus cultratus. (Petr and Mitrofanov, 1998).

While in arid and semiarid Asia the demand for irrigation water is still rising, the number of dams under construction is much lower than during the second half of the last century, largely because the majority of economically harvestable water resources has been already tamed. It is becoming evident, that irrigation needs to turn to more efficient water use methods. Overexploitation of water resources in arid regions of Central Asia, where water supply depends largely on snow and icemelt in distant mountains, has had a tragic consequences as documented in the desiccation of the Aral Sea and the loss of a major fishery there, which at its peak reached 44 000 tonnes per year. To replace such a quantity of fish through improved production from a diversity of inland waterbodies, almost all of which are now part of irrigation systems, is a major task and requires a major effort. Without a close collaboration among the countries of the region, including consultations and transfer of experience, it will be difficult to achieve such a goal.

Fisheries managers have to deal with conditions which are continuously changing under the priority demands for water resources, i.e. irrigation and hydropower. In their task they are assisted by fishery scientists from learned institutions, and with their help much work has been implemented to enhance fish stocks and to rehabilitate fisheries. Where fisheries in impoundments and whole irrigation systems are managed by a water authority in charge of all the multiple-functions of the valuable water resource, open dialogue among the stakeholders assists in a better understanding of the requirements for an efficient fish production.

In Central Asia the major strategy has been the introduction of fish and fish food organisms from the outside, both from Asia and Europe. Sometimes the reason for introduction was to replace an indigenous species of low or no fishery value by one or more easily adaptive and well-known fish such as common carp, pikeperch and Chinese carps. Far Eastern cyprinids (Chinese carps) have proved to be very adaptive, especially benefiting from clear waters of major irrigation canals and reservoirs. In a number of reservoirs the impact of fish introductions has been closely monitored, and an analysis of the data often led to more introductions. At present, there is probably not a single water body in the region left with only the original indigenous fish fauna, and introduced fish species may represent 50 percent or more in the total catch.

With the rising demand for fish in arid countries of Asia the need for a better management of water resources in irrigation systems is evident. Only in this way the fish production can increase, not only by enhancing the fish stocks in open waters through introductions and stocking, but also through the implementation of fish culture, such as cage culture, raceway culture and blocked-off cove culture. Special attention needs to be paid to fish production in saline waterbodies in the region and ways should be found how to reduce the concentrations of agrochemicals and other pollution of the residual waterbodies. Where swamps are used for such discharges, they should also be assessed for fish production. The possibility of using fish for the control of vectors of water-born diseases should also be taken into account, in some cases combined with the control of excessive growth of aquatic macrophytes as in irrigation canals. Elevating fisheries in irrigation systems from the often subordinated position to an equal partner in discussions and in the decision-making process should appear on the agenda of government deliberations dealing with irrigation systems.

Co-management and community-based management of irrigation waterbodies could be applied under the new privatization policy and market-oriented economies emerging in Central Asia. Maintaining and monitoring the fishery resource by a small group would facilitate exclusion of outsiders, often illegal fishermen. Government policy-makers may consider delegating the management responsibility to such collective or private groups, which then should receive government support through credit, training, scientific and extension assistance.

Outside Central Asia a number of countries in the dry zone faces the problem of how to best develop the wide range of waterbodies for fish production. Turkey has constructed a system of dams on the Euphrates and Tigris rivers that serves irrigation of large areas for agriculture production. The General Directorate of State Hydraulics in Turkey, which is in charge of the ever increasing number of reservoirs, has fostered the strategy of regular stocking of reservoirs with hatchery-produced fingerlings, largely common carp. In Keban and Karakaya reservoirs on the Euphrates the return on stocking has been 13 percent and 19 percent, respectively. During the 10-year period of 1982-1991, 20 million fingerlings were stocked into 115 reservoirs and 68 smaller waterbodies in Turkey, the majority of them having multipurpose function, including irrigation. Since then, at least seven more fish species are hatchery-produced for stocking (Petr, 1998). Pakistan and India have a sophisticated system of barrages, dams and irrigation canals. These countries have also made considerable progress in utilizing the irrigation systems for fish production. The expansion of wetlands in the Indus Valley and Indus delta in Pakistan is a direct result of the development of irrigation and river management. Cross (1994) noted that environmental assessment of water storage development in Pakistan has generally failed to take into account the positive value of the appearance of new wetlands.

Where there is irrigation, there is also seepage. Waterbodies from seepages from reservoirs and canals are not uncommon. Seepage from a dam can be utilized for hatcheries, ponds, or for raceways for production of trout, as for example in Iran and China (Petr, 1998). In Pakistan, a system of ponds has been constructed alongside the main canal diverting water for irrigation from Chashma reservoir on the Indus. Where seepage water accumulates under arid conditions with high evaporation rates saline waterbodies may form. In a suitable climate such "derelict" waterbodies can be used for culturing salt-tolerant species, such as tilapias.

The almost complete exploitation of surface waters in some arid areas of Asia is becoming a major obstacle to developing further areas under extensive furrow-type irrigation, which dominates irrigated agriculture in most of the countries. The central question confronting authorities is how to better utilize the existing water resources for the existing agriculture, and for its expansion. It is understood, that a fundamental change in agricultural use of water is needed, i.e. conversion from largely extensive agriculture, demanding high volume of water, to well-managed intensive agriculture based on low water demand. Shortening the flooding period in rice fields has had some negative impact on rice-fish culture in paddy fields in the Southeast Asia. As rice production is not the major crop in the arid belt of Asia, such a change may not affect the fish and fisheries in higher latitudes, where storages and distribution systems of canals will continue to represent the major waterbodies with fishery potential.

References

Cross, D., 1994. Getting wetter. New Scientist 1936: p. 51.

Ergashev, A.E., 1989. Central Asian irrigation canals and some aspects of their algal flora. Int. Rev. ges. Hydrobiol. 74: 83-94.

FAO, 1993. World Agriculture Toward 2000. FAO, Rome.

Kamilov, G. & Urchinov, Zh.U. 1995. Fish and fisheries in Uzbekistan under the impact of irrigated agriculture. FAO Fisheries Circular. No. 894: 10-41. FAO, Rome.

Karpova, E.I., Petr, T. & Isaev, A.I. 1996. Reservoir fisheries in the countries of the Commonwealth of Independent States. FAO Fisheries Circular. No. 915. FAO, Rome. 131p.

Kostyukovsky, V.L., 1992. Dynamics of Turkmenistan lowlands in conditions of natural and man-induced changes. Vodnye Resursy No. 4: 85-92. (In Russian)

Micklin, P.P., 1991. The water management crisis in Soviet Central Asia. The Carl Beck Papers in Russian and East European Studies No. 905. University of Pittsburg Center for Russian and East European Studies. 124p.

Mitrofanov, V.P., Dukravets, G.M. & Mamilova, R.Kh., 1988. Special features of the formation of the hydrocoenose in the Kapchagay reservoir on the River Ili. In: Impact of Agriculture on Biological Resources of Waterbodies in Kazakhstan, pp. 43-86. Izd. "Nauka" Kazakh SSR, Alma-Ata. (In Russian)

Mitrofanov, V.P., Dukravets, G.M. & Sidorova, A.F. 1992. Fishes of Kazakhstan. Vol. 5: Introductions and fisheries. Akad. Nauk Resp. Kazakhstan, Inst. Zoologii. ‘Gylym’, Alma-Ata. 462p. (In Russian)

Nikolaenko, V.A. 1988. Classification of water in reservoirs of Central Asia based on their chemical composition and their evaluation for irrigation use. Vodnye Resursy No. 2: 115-121. (In Russian)

Pavlovskaya, L.P. 1995. Fishery in the lower reaches of the Amu-Darya under the impact of water manipulation for irrigated agriculture. FAO Fisheries Circular. No. 894: 42-57. FAO, Rome.

Petr, T. 1992. Lake Balkhash, Kazakhstan. Internat. J. Salt Lake Research 1: 21-44.

Petr, T. 1995. Fisheries in irrigated areas of Central Asia. FAO Fisheries Circular. No. 894: 1-9. FAO, Rome.

Petr, T. 1998. Fisheries in reservoirs in the arid and semiarid zones of Asia. Internat. Rev. Hydrobiol. 83 (Special Issue): 591-598.

Petr, T. & Mitrofanov, V. P. 1998. The impact on fish stocks of river regulation in Central Asia and Kazakhstan. Lakes & Reservoirs: Research and Management 3: 143-164.

Pircher, W. 1993. 36 000 dams and still more needed. Water Power & Dam Construction, May 1993: 15-18.

Salikhov, T.V. & Kamilov, B.G. 1995. Ichthyofauna of the mid-Syr-Darya basin. J. Ichthyol. 35: 61-71.

Sanin, M.V. & Shaporenko, S.I. 1991. On the use of drainage waters for fisheries. Vodnye Resursy No. 4: 147-152. (In Russian)

Walker, K.F. & Yang, H.Z. 1999. Fish and fisheries in western China. FAO Fisheries Technical paper. No. 385: 237-278. FAO, Rome.