THE USE OF IRRIGATION SYSTEMS FOR SUSTAINABLE PRODUCTION OF AGRICULTURAL AND FISH PRODUCTS IN THE REPUBLIC OF KAZAKHSTAN

by
Khismet Ismukhanov
Kazakh Scientific and Research Institute of Fisheries, 480016.89^A,
Suinbai Str., Almaty, Kazakhstan
and
Valiakhmet Mukhamedzhanov
Kazakh Scientific and Research Institute of Aquaculture,
484022.12, Kolbasshi Str., Taraz, Kazakhstan

Abstract

Kazakhstan has 8 large river basins. The total annual water discharge in Kazakhstan is 100.9 km³ of which 56 km³ originates in the country itself, with the rest coming from the neighbouring countries. The available water resources (minus those needed for maintaining good water quality and for ecological needs) represent 42.6 km³ per year. Of the annual use of 42.6 km³ of water over 70 percent is used for irrigation. Irrigated farming is essential for food production in Kazakhstan. In Kazakhstan approximately one third of agricultural plant production comes from the irrigated lands which represent about 5-6 percent of the farmed area. Irrigated farming predominates in the south of the country where cotton is produced on 36.6 percent (i.e. 2.3 million ha [mha]) of the irrigated area, forage crops on 17.8 percent, cereals on 14.5 percent, vegetables and other cultures on 29.1 percent. To store water for irrigation, many rivers, in particular the large ones, are regulated by dams. This allows both long-term and seasonal regulation. There are 475 reservoirs in Kazakhstan and more than 96 000 km of irrigation canals at present. In the southern regions of Kazakhstan there are 75 reservoirs with a total capacity of 95.5 km³ and surface area of over 10 000 km². The great majority of large reservoirs are multipurpose. Reservoirs play an important role in fisheries. Among the large reservoirs, fisheries are well developed on the Bukhtarma in the north, and on Chardara and Bugun in the south. Thirteen fish hatcheries-cum-fish farms have been constructed and currently operate in Kazakhstan. Most of them are adjacent to reservoirs, including Bukhtarma and Kapshagay, and they produce fish for stocking the reservoirs. They have played a significant role in enhancing stocks of common carp and silver carp. Lately, economic problems in the country have led to a deterioration of irrigation systems, including pumping stations, and the undergoing process of transition to market economy has interfered with the formerly efficient and well-organized fisheries. As a result, the catches have been declining, fish stocks are often harvested illegally and reservoir-associated hatcheries are facing shortages of funds and cutting down on the number of stocking material produced. The great fisheries potential of numerous waterbodies is thus poorly utilized at present.

1. Irrigation farming systems in Kazakhstan

1.1 Water resources

Irrigated farming is essential for food production in Kazakhstan. Prior to transition to the market economy approximately one third of agricultural products came from irrigated lands, although this represented only 5-6 percent of the farmed area. In southern Kazakhstan the produce from irrigated farming often represented 2/3 of the total produced in Kazakhstan. Over 70 percent of water is used for irrigation. At the same time the efficiency of production per irrigated hectare does not reach the optimum level.

The efficiency of irrigation farming and its further development in Kazakhstan are determined mostly by the availability and quality of water resources. Rational use of water resources is a top priority. The ever growing demand for water and the continuing deterioration of water quality resulting from pollution of all kinds require urgent and efficient measures to safeguard sustainable development of agriculture and fisheries and other important sectors of the national economy.

While areas suitable for irrigated agriculture cover about 5 mha of land, water resources of Kazakhstan, especially in the south, are limited. There are 8 large river basins and more than 96 000 km of irrigation canals. The total annual water discharge in Kazakhstan is 100.9 km³ of which 56 km³ originates in the country itself, with the rest coming from the neighbouring countries. The available water resources (minus those needed for maintaining good water quality and for ecological needs) represent 42.6 km³ per year (Table 1).

Table 1
Water resources of Kazakhstan

The limited water resources place constraint on further development of agriculture, and shortage of water resources in drought years leads to restricted water supply in some parts of the country. This takes place when water resources of most river basins in the country are either exhausted (basins of the rivers Syr-Darya, Shu, Talas, Ili, etc.) or almost exhausted.

The shortage of water resources leads to the use of return waters for irrigation. Under "return waters" is understood the part of irrigation water which returns from irrigated land back to the river or is discharged into a depression or a lake without an outflow. Return waters result in degradation of flora and fauna and in pollution of surface water resources as they contain higher concentrations of salts, fertilizers, herbicides and other harmful chemicals, as well as higher concentration of bacteria than water present in unpolluted rivers. An example of this is the deterioration of water quality in the Syr-Darya River under the impact of return waters.

To accurately estimate the quantity of return waters entering a river is not easy. During the period 1986-1995 an average annual volume of the non-return water resources used in the Syr-Darya River basin was estimated at 23.86 km³ per year, with annual fluctuations from 18.79 to 24.27 km³ per year. In Kazakhstan the average value was 6.28 km³ per year.

In the Syr-Darya River basin 8 160 m³/ha of freshwater is used for irrigation. In the upper reaches of the river (Kyrgyzstan, Uzbekistan) it is less, with only 6 320 m³/ha used (range 5 760-7 170 m³/ha). The maximum is used in the middle course and the lower course of the river (in Kazakhstan), with a range from 8 290 m³/ha to 13 560 m³/ha.

Poor technical conditions of Syr-Darya irrigation systems necessitate the use of return water, of which currently over 10 km³ is used, including the 3.2 km³ formed within Kazakhstan. Large volumes of return water were used especially during 1975-1997. This has been followed by a slow decrease as a result of the reduction of the area of irrigated lands and consequently also the volume of irrigation water required. The neighbouring countries Uzbekistan and Kyrgyzstan continue to produce considerable volumes of return water which is being discharged into the Syr-Darya and reaches Kazakhstan. This results in the deterioration of the quality of irrigation water and aggravates the ecological and epidemiological situation in the Syr-Darya catchment.

The use of return water and freshwater (non-return water) in irrigation systems of southern Kazakhstan and in Kyzylordinsky Oblast (=Province) during 1990-2000 is shown in Table 2.

Many rivers, in particular the large ones, are regulated by dams. This allows both long-term and seasonal regulation. There are 475 reservoirs in Kazakhstan at present. The characteristics of the major reservoirs are given in Table 3. In the southern regions of Kazakhstan there are 75 reservoirs with a total capacity of 95.5 km³ and surface area of over 10 000 km². This includes 22 reservoirs of long-term regulation. The capacity of 11 reservoirs exceeds 100 million m³ (Mm³)^. The great majority of reservoirs are multipurpose. In eastern and northern Kazakhstan their first priority is hydropower production, in northern Kazakhstan they also provide water supply for cities and towns and for industries and support fisheries, in the south they serve mainly irrigation and fisheries, and in western Kazakhstan in the area between the Ural and the Bolshoi Uzen rivers they serve irrigation.

1.2 Irrigation farming

Irrigation farming is the main consumer of water. Its share is more than 70 percent of the total water intake. Some decline in water consumption has been observed. Compared with 1990 the total water consumption has decreased by 42.6 percent, with a 33.9 percent decrease in agriculture.

Table 2
Average annual volumes of the use of non-return and return water resources in irrigation systems of the Syr-Darya River basin in Kazakhstan

Irrigation farming in Kazakhstan, especially in its southern regions, has come a long way, from the primitive irrigation ditches, aryks, to the most complex modern engineering systems with elements of automatization. By the beginning of the 1990s the area of irrigated lands alone exceeded 2.3 mha. Improvement funds and the share of products from irrigated areas reached almost one third of the gross production output of farming.

Table 3
Characteristics of the major reservoirs of Kazakhstan

In many drought-prone regions of Kazakhstan it is not possible to maintain agricultural production without irrigation. Being one of the main directions of land melioration, irrigation permits land productivity to increase significantly. Irrigation is especially effective in southern Kazakhstan. It is known that irrigation increases crop yields 3-7 times compared to those produced on non-irrigated areas in the desert and semi-desert climate. Irrigation farming makes it possible to grow higher value crops such as sugar beet, cotton, rice, vegetables, melons, fruits and berries. By percentage cotton, with 38.6 percent of the total, dominates the crops produced using irrigation in southern Kazakhstan, followed by animal feed crops (17.8 percent), cereals (14.5 percent), vegetables (9.5 percent), and other crops (19.6 percent). Rice is cultivated on about 70 000 ha in three Oblasts of Kazakhstan.

Irrigation farming reached a maximum surface area in 1986 with regular irrigation of 2.4 mha. At that time 1.034 mha were irrigated in the estuary of the Syr-Darya. After that the productivity of irrigated lands decreased (Table 4).

Table 4
Crop yields on irrigated lands in southern Kazakhstan (tonnes/ha)

At present the area of irrigated lands totals 2.36 mha. Only 1.38 mha are in a good condition, i.e. about 60 percent of irrigated lands. The collector-drainage system is used on a small part of irrigated lands. Lands are irrigated mainly by a surface method. There is a low level of mechanization. Overhead irrigation is used on an area of about 660 000 ha. There are 96 387 km of irrigation canals, of which 20 620 km are lined, and 9 467 km are pipelines. The length of the collector-drainage system is 14 902 km. In recent years there has been no further development of the irrigation agriculture, rather deterioration of the existing structures due to the virtual absence of government financial support. This reflects the deterioration of the overall economic situation in agriculture. Almost one million hectares of irrigated lands are now out of production, there has been an increase in poor practices of water use and construction and rehabilitation have been suspended. As a result, irrigation systems as well as the quality of lands are gradually deteriorating.

The cultivated irrigated lands have been reduced by 880 000 ha, i.e. 43.4 percent, over the last five years. There have also been considerable changes in crop production. By 1997 cultivation of livestock feed crops had been reduced by more than 2.7 times; sowing areas of vegetables, melons and potatoes by 2.2 times, and non-food crops by more than one third. Where formerly cereals were grown on 30 percent of irrigated areas, today they are produced on almost 50 percent of them.

Changes in irrigation over the period 1970-1990 in Kazakhstan are shown in Tables 5 and 6.

Table 5
Changes in irrigation farming in Kazakhstan

The main irrigated areas are located in four southern Oblasts under drought conditions: Kyzylordinsky Oblast - 285 900 ha, South Kazakhstan Oblast - 500 500 ha, Zhambylsky Oblast - 248 200 ha, and Almaty Oblast - 665 900 ha. In total they occupy 1.7 mha out of the total of 2.2 mha of irrigated areas in all Kazakhstan. As for the other regions, the Eastern Kazakhstan Oblast has the largest irrigated tracts of lands of 220 000 ha.

Further expansion of irrigated lands faces two major constraints: the unfavourable social and economic situation in the country which is slowing down investment in the development of water resources, and chronical shortage of water in some areas. At present there exists no integrated management programme for the development of water and land resources for a number of river basins.

Table 6
Main indicators of the use of water resources in Kazakhstan, 1995-1998

Government policy for the near future should first of all concentrate on the rehabilitation of irrigation systems but at the same time decisions should be made on how to optimally use water and land resources. This would allow the maintenance of the existing lands under irrigation.

Land ownership transfer from the state to private ownership can be considered as completed. Further work in this direction should deal with structural reconstruction of the entire water resources sector within the framework of social and economic reforms. The whole complex of issues includes considerations dealing with the transboundary water allocation in southern Kazakhstan.

1.3 Technical level of meliorative systems

Melioration and rehabilitation of irrigated lands have been virtually suspended during recent years. As a result, the engineering and technical level of a considerable part of irrigation systems is such that it hinders their normal functioning.

Reduced funds and deterioration of irrigation systems prevent efficient use of water and land resources and this has led to a large reduction in the crop and fodder production from irrigated lands.

The collector-drainage network is poorly developed on all irrigation systems (it does not exceed 2.14-3.26 linear m/ha). This results in waterlogging and increasing salinity of the soil. Especially difficult is the situation in southern Kazakhstan with the rotation of rice and cotton. Timely planned and continuing maintenance and repairs of the network would lead to increased efficiency and reduced losses of irrigation water, probably saving up to 40 percent of water intake. A reduction of the total water intake for irrigation would make it possible to increase the river flow in the river basin’s lower reaches. And this in turn would allow better irrigation of floodplains and stop the processes of degradation of the environment. This is important because free-range livestock grazing plays an important role in the agricultural production of the country. Its further development depends on the availability of good pastures.

1.4 Quality of water resources

Irrigation farming is the main source of water pollution. This is due to the use of return water which is discharged back into the river, where it mixes with good quality water, to be re-used for irrigation further downstream. The self-purification property of rivers is reduced, sometimes to a level that endangers aquatic life. The polluted and salinated water may also enter the ground water. When water with increased salt concentration is used for irrigation, this - depending on the salinity of such water - will lead to a decline in crop production. Most irrigation water is used for cultivation of rice and cotton. Return waters from these tracts of land are characterized by a wide range of chemical components and high levels of salts (1.0-5.0 g/litre), ammonium nitrogen (0.6-5.0 mg/litre), pesticides (up to 10 times the maximum allowable concentrations). Some waters in southern Kazakhstan no longer meet water quality standards for domestic and industrial use. This has an impact on health of the people inhabiting the areas so affected.

On average the annual net water volume intake is 20-25 km³ and it is almost fully used. About 75 percent of water intake is used by agriculture, mainly for irrigation. Cultivation of rice and cotton leaves about 25-35 percent as return water to be drained away. This water is enriched in nitrogen resulting from the application of ammonium sulphate, which is removed mainly as nitrate. Its maximum values in water are reached after the application of fertilisers. Nevertheless, water in the major rivers of Kazakhstan is classified as being only slightly polluted.

2. Fisheries in irrigation systems of Kazakhstan

Kazakhstan is a country with large and diverse water resources. They include northern and central parts of the Caspian Sea, the northern part of the Aral Sea, the large lakes Balkhash and Alakol, hundreds of reservoirs including the largest Bukhtarma (which includes the large lake Zaisan) with an area over 5 000 km³, tens of thousands of medium-size and small lakes and rivers including the Irtysh, Ural, Syr-Darya and Ili.

The availability of such large diversity of waterbodies has stimulated the development of fisheries. When compared with agriculture, fisheries is a relatively young branch of Kazakhstan economy. Its intensive development commenced only in the 1960s. The fisheries targeted the Aral Sea and river fish stocks, and reservoir fish stocks. Fisheries management measures included introductions of new fish species, hatchery production of stocking material and introduction of fish food organisms. New fish processing factories, fish pond farms, lake farms and other enterprises producing stocking material of valuable fish emerged.

All those efforts led to a more than threefold increase in fish production in the country and by 1975 fish catches reached a maximum of 100 000 tonnes (Table 7). It should be emphasized that the valuable sturgeons represented a considerable share in catches. Annual black caviar production reached 885-1 239 tonnes during those years. More recently, as a result of deterioration of ecological conditions on the Caspian Sea, commercial sturgeon fish stocks have dropped dramatically. Today the annual catch is about 250 tonnes.

Table 7
Fisheries production (thousand tonnes) in Kazakhstan by Five-Year Plans

Reservoirs play an important role in fisheries. Smaller reservoirs (Table 8) range from several hundred to several thousand hectares and they are used mainly for irrigation, domestic and industrial water supply. Only a small part of the large number of small reservoirs is multipurpose.

Hydroelectric power stations were constructed on five large reservoirs, i.e. Bukhtarma, Chardara, Kapshagay, Shulbin and Ust-Kamenogorsk. Reservoirs located in the north of the country are mainly for power production, water supply for industries, and for fisheries. They are rarely used for irrigation. Reservoirs in the south serve mainly irrigation.

Among the large reservoirs fisheries are well developed on the Bukhtarma in the north, and on Chardara and Bugun in the south.

Table 8
Major reservoirs in Kazakhstan

Bukhtarma reservoir was constructed on the Irtysh River in 1960, flooding and enlarging Lake Zaisan. The seasonal drawdown is negligible: in spring (May) within 15-20 days there is a high-water discharge of up to 2.5-3.0 km³ for irrigation of grasslands in the low-lying Pavlodar Oblast. More recently, in connection with the construction and commissioning of the Shulbin hydroelectric power station, the volume of the spring discharge has been reduced considerably. The relatively stable level of Bukhtarma reservoir promotes successful spawning of fish. During the first years of the reservoir the fish stocks mainly consisted of fish of low value, such as roach, ruff, perch and some other species, which represented over 70 percent of the total catch. To enhance the quality of fish stocks, fish species of higher value were introduced, especially during the first several years. Of these zander (Stizostedion lucioperca), bream (Abramis brama), European cisco (Coregonus albula) established themselves and became a regular component in commercial catches. Fish food organisms from lakes Onega and Baikal and from the Caspian Sea were also introduced and now form a valuable component of fish food.

All this, in combination with the new fishing regulations, permitted a twofold increase in fish catches by 1974-1975 as compared with the first years. Fish catches reached a maximum of 12 700 tonnes in the Bukhtarma (Table 7), with a fish yield of 26.0 kg/ha. At the same time the share of poor value fish species decreased to 16 percent while the introduced species made up over 80 percent of the total catch.

Some fish losses are incurred during their passage through turbines of hydroelectric stations because there are no fish protection installations to prevent this. However, this has little impact on fish stocks because in Buktarma reservoir the water intake is more than 60 m below the water surface.

Water pollution, including pesticides, organochlorines, heavy metals and oil products, have an adverse impact on aquatic organisms, but the maximum values do not exceed the maximum allowable concentrations.

Chardara reservoir was constructed for irrigation and hydropower production in 1965 on the middle course of the Syr-Darya. Like a majority of irrigation reservoirs in southern Kazakhstan, Chardara is filled in the autumn-winter period (October-March) and drawdown takes place in spring and summer (April-September). Seasonal fluctuations of the water level reach up to 11 m. During the spring and summer the drawdown reduces the reservoir surface to only 15 000- 20 000 ha, which is a quarter or less of the water surface area of the full reservoir. At the same time the water volume is reduced 10-12 times. Such considerable seasonal changes in the volume and the surface area are mainly due to the irrigation water uptake. Water for irrigation enters Kyzylkum Canal, but some water is also used for power generation.

The ichthyofauna of Chardara reservoir formed from the indigenous species of the middle course of the Syr-Darya. From the 33 introduced fish species, 20 species are not present in the reservoir, but 12, including common carp, crucian carp, bream and zander (pike-perch), are of commercial importance. Regular fishing commenced in 1968. During the first eleven years (1968-1978) annual fish catches increased from 400 tonnes to 1 800 tonnes, with an average catch of 1 000 tonnes per year. Bream (52.2 percent) and common carp (22.7 percent) dominated. The largest volume of bream was recorded during 1980-1991, zander occupied second place and common carp third. Annual catches fluctuated from 1 340 to 1 940 tonnes, averaging 1 720 tonnes per year. Commercial fish yield fluctuated from 22 kg/ha to 39 kg/ha, averaging 30 kg/ha.

The most important factors influencing the fish stock formation in Chardara reservoir are hydrological regime which is determined by water uses other than fisheries, hydrochemical regime, and fishery. Reduction of the surface area and shallowing leads to the reduction in the number of spawning areas and to a high mortality of the spawn during the spring breeding period (April 1-May 20). In summer months fish may die due to low concentrations of dissolved oxygen resulting from blue-green algal blooms. Reservoir drawdown also considerably reduces the habitat of benthic organisms and changes their species representation. Benthic organisms are an important food source for some fish species. By autumn, with the drop in water temperature the situation worsens, especially for plankton. There is also a loss of valuable fish species such as zander, roach and bream due to the fry being carried out into the Kyzylkum Canal. In May the maximum number of fry are washed out, with an estimated loss of one million per day. However, the reproductive potential of the fish species still allows an annual fish harvest of 400 to 1 800 tonnes.

Starting in 1992 there was a change in the schedule of the use of the reservoir. The upper part of Chardara reservoir was now located in Uzbekistan. In 1992-2000 high discharges of the Syr-Darya from February to April led to water spilling over the Chardara spillway as well as over the Arnasay emergency spillway. Large quantities of fish fry and fish of all age groups were washed out. The outflow of 800-1 600 m³/sec over the emergency sluice resulted in great fish losses. It is estimated that during those two months, from 1992 to 2000, annual losses of fry of valuable fish species reached 18 to 64 billion. Taking into consideration that the commercial fishing pressure has not changed during the last ten years and the impact of other factors has not changed either, one can assume that the loss of fry and larger fish during floods was responsible for the sharp drop in catches of commercial fish species, from 2 040 tonnes in 1992, to 216 tonnes in 1999.

The following measures are suggested to reduce the rate of fish loss and to increase the stocks of valuable commercial fish species: reconstruction of the Kyzylkum sluice; relocation of the water intake deeper than at present; and construction of a fish protection device on the Arnasay emergency spillway. It is also planned to construct a new reservoir (Koksarai) 120 km distant from Chardara reservoir, to store flood waters which now end in Arnasay.

Since the 1980s the reservoir water has been polluted with pesticides, and this has led to fish mortalities. Over a ten-year period it is estimated that 865 tonnes died because of that. In the more recent years fish mortality has rarely been observed during the pre-spawning and spawning periods as concentrations of pesticides and herbicides have declined as a result of the reduced use of these agrochemicals.

Low value fish species such as silver carp have recently dominated the catches. It is believed that this is because of mass mortalities of common carp during the period 1980-1990, resulting from pesticide poisoning.

The ratio among fish species is continuously changing, with appearance of new species. The recent dramatic reduction in stocks of valuable commercial fish species requires major rehabilitation measures. These include limits on the catch or even closing of the fishery, and intensive stocking of the reservoir with fish species of high value. It has been proposed to intensify stocking of one-year-old common carp, which in four year time should lead to a sustainable carp harvest of 300 tonnes/year. An attempt to close the carp fishery during the period 1997-2000 failed because of lack of enforcement. Low value fish species should be controlled by intensive fishing to reduce the pressure on fish food organisms. This would make them available for fish species of a better value.

Prior to the regulation of the Syr-Darya River the introduced Chinese herbivorous carps were already reproducing in the river. Silver carp entered the Syr-Darya from fish ponds located at Kairakkum reservoir in Uzbekistan. By 1970 the fish were 4-6 year old. In the reservoir they reached commercial quantities for the first time in 1974 when they became a common component of fish catches. To increase their stocks it was recommended to stock reservoir every year with 250 000 two-year-old fish.

Herbivorous fish undertake regular spawning migrations to spawning areas. Recent studies show that 11 000-30 000 (equal to 70-300 tonnes) of silver carp migrate for spawning in the inflowing rivers. Downstream drift of spawn of silver carp takes place in late April, early May. There are no one-year-old fish in the reservoir. This indicates that commercial stocks of silver carp form at the expense of the fish escaping from fish ponds. Over 250 000 fry may have arrived this way, and others drift in from the upstream situated reservoirs and farms on the Syr-Darya in Uzbekistan. According to estimates based on data from trawling surveys, in the year 2000 commercial stocks of silver carp were 74.2 tonnes. As there is a high mortality of spawn drifting into the reservoir it is recommended to collect seed in the Syr-Darya and grow it in ponds to a size suitable for release into the reservoir. This should also increase the reservoir fish production and reduce the pressure on hatcheries which breed stocking material from broodstock kept in fish farms. It is believed that in order to provide a sustainable harvest of 100-120 tonnes, the current stocking rate should be increased 3-4 times.

Bugun reservoir is the second largest irrigation reservoir in southern Kazakhstan. It is located in the valley of the Bugun River in the South-Kazakhstan Oblast. It receives water from the Bugun and Arys rivers. The dam is 5 km long, with a height of 17 m, resulting in a maximum reservoir depth of 15 m. The average depth is 5.8 m when full, and 1.4 m at a minimum water level. The reservoir is 13.5 km long and 5.7 km wide. The reservoir fills in autumn and winter and drawdown takes place in spring and summer. Water level fluctuates by up to 10 m. During the three summer months the reservoir loses three quarter to four fifth of the accumulated winter water and its water surface area is reduced to 15 percent of that when full. Bugun reservoir is a classical example of contradiction between the needs of irrigated agriculture and fisheries: irrigation requires drawing water in spring when an increase in water level is in the interest of fishery as fish start to spawn.

During the first years the reservoir fish catches were high and yielded 70 to 80 kg/ha. The total catch was 250 to 360 tonnes/year. Common carp was the major fish species caught, forming 77 percent to 89 percent of the total. Subsequently the fish catches begun to fall rapidly as a result of unfavourable water level fluctuations which had a negative impact on spawning and nursery grounds. The 1977 total catch was 365 tonnes, but in 1979 it was only 101 tonnes. Large fry losses of especially common carp resulted from spilling and pumping. While fish species composition has not changed, there were changes in the species dominance in catches. The present fish stocks in Bugun reservoir are represented by silver carp, crucian carp, eastern bream (Abramis brama), zander, asp, wels (Silurus glanis), bighead carp, and roach.

By the end of the 1970s fish stocks in Bugun reservoir were very much reduced due to the unfavorable water level during the reproduction period and due to losses of fry pumped into the irrigation canals. The 1982-1984 annual catch ranged from 50 to 96 tonnes, and the yield declined to 14.2-27.4 kg/ha. To enhance the fish stocks, starting in 1985 the reservoir was stocked with fish produced in a hatchery cum fish farm, constructed in the vicinity. The major fish species stocked were common carp and silver carp. As a result the annual catch begun to increase and reached 278 tonnes by 1988. But the release of 650 000 yearlings of common carp during the period 1985-1987 did not make much difference in catches. The high water discharges and the lack of fish protection devices are blamed for an increase in fish losses from the reservoir, with fish entering the major irrigation canal. If such losses are prevented, the stocking would become effective. It is estimated that annual stocking of the reservoir with approximately one million of one- and two-year-old common carp and 200/ha two-year-old silver and bighead carp would result in a 30 percent increase in catches, increasing the annual catch by up to 75 tonnes.

The following two approaches have been identified as the most important for increasing the commercial fish stocks using the existing natural fish feed supply in the reservoir:

• installation of fish protection devices on water discharge into the Turkistan Canal, and

• stocking of the reservoir with two-year-old common, silver and bighead carps.

3. Discussion

Fish protection devices were not envisaged under the construction of multipurpose or irrigation dams. This contributed to the disappearance of many valuable fish species initially present in reservoirs, as they were lost in irrigations canals, spilled into depressions, or - in the case of the northern reservoirs - passed through the turbines and spilled. No doubt many species also could not adapt to the sudden change from river to reservoir conditions. The following fish species became very rare or disappeared: Siberian sturgeon (Acipenser baeri), nelma (inconnu) (Stenodus leucichthys), and ide (Leuciscus ide) in Bukhtarma reservoir; ship (Acipenser nudiventris) and Balkhash marinka (Schizothorax argentatus) in Kapshagay reservoir; ship and Aral barbel (Barbus brachycephalus) in reservoir. Installations of fish protection devices is considered to be in the interest of the fisheries.

Thirteen fish hatcheries-cum-fish farms have been constructed and currently operate in Kazakhstan. Most of them are adjacent to reservoirs, including Bukhtarma and Kapshagay and they produce fish for stocking reservoirs. They play a significant role in enhancing stocks of common carp and silver carp. Annually 40 to 50 million fry and fingerlings of such species are released, in addition to some 300-400 million fry of European cisco and peled (Coregonus peled).

Small reservoirs in Kazakhstan, ranging from several hundred to several thousand hectares, are used for irrigation, industrial and domestic water supply. They also have extensive fisheries, but largely of a recreational character. Studies of small irrigation reservoirs in southern Kazakhstan (Almaty Oblast) showed that they have good production potential when stocked with one-year-old common carp, grass carp and silver carp in polyculture. Better utilisation of small reservoirs is at present hampered by shortage of stocking material.