The drying of the Aral Sea has been accompanied by a profound degradation not only of its own ecological system but also of those neighbouring on it. The ecological degradation became especially critical east of the Aral Sea, in the lower reaches of the Amu-Darya and the Syr-Darya where the Republic of Karakalpakstan, the Khorezm Region of Uzbekistan, and the Tashauz Region of Turkmenistan are situated. This was the direct impact of water resource manipulation through the construction of dams and barrages and diversion of water for predominantly irrigation use. There has been a change in fish stocks of the major rivers, with sturgeon, shovelnose and Aral trout virtually disappearing from them. While formation of reservoirs provided new environment for lacustrine fish species, these had to be introduced, largely from the Far East. Pollution through agrochemical inputs has caused a major problem especially in the drainage-fed water bodies, such as the Sarykamysh Lake, where most of the fish are declared unsuitable for human consumption. The lakes based on receiving drainage waters are also undergoing a process of gradual increase in water salinity, which eventually makes the environment unsuitable for the great majority of freshwater fish species. The future of the fishery in the lower Amu-Darya depends much on solving the problem of the Aral Sea and its catchment. Only implementation of a water resource rehabilitation programme could lead to the rehabilitation of fish stocks and fisheries. Some of the measures such as redistribution of the water resources and improvement of water quality can be achieved only as a result of international collaboration of all countries of the Aral Sea basin, i.e. Karakalpakstan, Turkmenistan, Uzbekistan, Kazakhstan, Kyrgyzstan and Tajikistan.

The Aral Sea Basin is one of the oldest regions of irrigated agriculture where the favourable climatic conditions and natural fertility of the soil favour the development of agriculture. Until the 1950s, irrigation water demands were relatively low with the major water supplying rivers, i.e. Amu-Darya and Syr-Darya regularly discharging into the terminal lake, the Aral Sea. Since the 1960s, however, when the states of Central Asia (Uzbekistan, Turkmenistan, Tajikistan, Kyrgyzstan) and Kazakhstan initiated a large-scale opening up of new lands through irrigation the equilibrium between the water demand of man for the water and that required for a healthy functioning of aquatic systems, has become destroyed. It took only about 30 years to develop into a major ecological crisis of the Aral Sea Basin.

The ecological degradation became especially critical east of the Aral Sea, in the lower reaches of the Amu-Darya and the Syr-Darya where the Republic of Karakalpakstan, the Khoresm Region of Uzbekistan and the Tashauz Region of Turkmenistan are situated. While great damage was caused to the whole economy of the area, the fishery in the lower Amu-Darya suffered the greatest damage. In good years the Aral Sea fishery produced close to 40 000 t of which the South Aral produced 25 000 t and about 98% of all fish output of Uzbekistan. More than 90% of the catch represented economically valuable freshwater fish, i.e. bream, carp, roach, barbel, and wels. The share of the Aral Sea in the total catch from inland water bodies of the ex-USSR was only about 5%, but it took second place after the Caspian Sea in the economic fish catch. The fish came predominantly from the Aral Sea but also from lakes of the deltas of the two major inflowing rivers, Syr-Darya and Amu-Darya.

Water manipulation of rivers, construction of dams and barrages and diversion of water for predominantly irrigation uses have led to a decline in the Aral Sea water level, and to an increasing salinity. Lakes in the delta and floodplains started to dry out as a result of diversion of water into irrigation canals. All this has led to changes in the aquatic environment. As a result, fish stocks of economic importance either completely disappeared, as in the Aral Sea, or declined, and in some situations have been replaced by low-value fish.

2. IMPACT OF HUMAN-INDUCED CHANGES ON THE BIOTA OF THE ARAL SEA

The drying of the Aral Sea has been accompanied by a profound and perhaps irreversible degradation of its ecological system. As its water level started declining, the Sea has gradually become sub-divided into two halves, i.e. Greater Sea and Smaller Sea, with (in 1991) surface areas of 33 840 km², and 2 800 km² respectively. The salinity in the Greater Sea reached 35 ppt and in the Smaller Sea 30 ppt. In 1991, the sea level reached 37.3 m a.s.l. The impact of water uptake for irrigation from the Amu-Darya can be followed from the total annual discharges, as measured between 1959-1992 in the middle course at Kerki, and in the mouth of the Amu-Darya at Kzyljar (Fig. 1). Before the full development of the irrigation system the irreversible uptake represented about 25 km³/year. This has markedly increased since 1970 with the annual uptake reaching 50 km³/year or even more. In some years, no water from the Amu-Darya reached the Aral Sea.

The total discharges (i.e. from the Syr-Darya and Amu-Darya) into the Aral Sea have always been irregular. But again, a rapid drop can be seen in 1970 and the following years. Intensification of irrigation has led to a situation when the total annual discharge into the Aral Sea almost never exceeds 20 km³, and in 1981-1989 ranged between 0.9 and 9.5 km³ only, except in 1988 when 23.8 km² reached the Aral Sea as a result of an exceptionally high rainfall in the catchment (Fig. 2). The average long-term total average discharge in the Aral Sea, based on data for the period 1911-1960, was 56 km³/year.

The drying of the Sea (Fig. 3), accompanied by a gradual salinity increase, has led to changes in biological diversity and to a decline in the total fish biomass. The increase in salinity from 10.2 ppt (in 1961) to 35 ppt (in 1991) led to the extinction of freshwater animals which represented the core of the Aral endemic fauna.

The present composition of aquatic invertebrates (zooplankton and zoobenthos) in the Aral Sea is represented by a small number of euryhaline species of sea origin and the halophilic species of inland waters (Anon., 1991). The biomass is dominated by the Calanipeda aquaedulcis Kritsch., Nereis diversicolor O.F. Muller, Syndosmya segmentum Reclus, Arba ovata Phil., and Palaemon elegans Rathke. From the typical Aral fauna only Synchaeta, Halicyclops rotundipes aralensis Bor., and Cerastoderma istmicum Issel remain. In the Greater Sea is also present Rhithropanopeus harrisii tridentata Maitland, introduced from the Azov Sea. With a further increase in salinity most species are likely to disappear as can already be seen in the northern bays (Anon., 1991) where the salinity increases much faster than in the main water body.

By the mid-1980s all 20 endemic fish species of the Aral Sea disappeared except for Pungitius platygaster (Kessl.). The fishery completely stopped in 1982. At present, apart from the above species, there are four species, all introduced: flounder Platichthys flesus luscus, herring Clupea harengus membras, sand smelt Atherina mochon caspia and monkey goby Neogobius fluvitatilis pallassi. The flounder was stocked between 1979 and 1987 and in 1991 more than 100 t of this fish was caught in the Smaller Sea. The increase in flounder in the rest of the Sea led to a recommendation to fish commercially on a pilot scale in the western part of the Greater Sea (Zholdasova et al., 1992). In spite of the ability of the flounder to tolerate high salinities of up to 60 ppt, its presence in the Aral Sea may still be limited because the salinity of the Sea is still increasing, and this affects negatively the species composition and number of organisms such as crabs and shrimps on which the flounder feeds.

The profound changes in the biota of the Aral Sea can be summarized as: decline in the number of endemic species, and establishment of the introduced and predominantly euryhaline species. Establishment of the flounder in the Sea shows that the management measures were successful and well thought out. In 1991 the Kazakh scientists proposed the introduction of grey mullet (Mugil soiuy Bas.). However, the re-birth of fishery will depend on whether there is no further increase in water salinity. This could be achieved if water discharges into the Azov Sea are maintained at least at the rate of 30 km³/year.

During the last 30 years the Amu-Darya waters have been used for large-scale irrigation. For this purpose, many irrigation canals were constructed, among which the largest were the Karakum canal, delivering 300 m³/sec, and the Karshi and Amu-Bukhara canals delivering about 100 m³/sec each. Apart from these there exist hundreds of smaller canals and pumping stations supplying and distributing the Amu-Darya water to irrigated fields. A number of water storage reservoirs also appeared. As a result, an almost 100% irreversible use of water was achieved, leaving very little, if any water to reach the Aral. For the fish of the river, the impact of human measures has also been far reaching.

The Amu-Darya and Syr-Darya were important spawning habitats of two migrating fish, the Aral sturgeon Acipenser nudiventris and Aral bream, whose spawning sites were up to 1 000 km distant from the Aral Sea. The young fish then returned to the sea to feed and mature before they started migrating upstream.

The chemical composition of the river water has changed under the impact of the discharges of drainage waters from irrigated fields and from industries. Between 1960 and 1989 the Amu-Darya's average salinity increased from 540 mg/l to 1 161.2 mg/l, with 856.6 mg/l measured in 1990. The increase can be seen when comparing the middle course with the Amu-Darya water salinity just before reaching the Aral Sea: at Termez it was 653.2 mg in 1990, at Nukus in 1990 - 946.8 mg/l. The chemical character of the Amu-Darya water has changed from calcium-carbonate dominated to sodium or potassium chloride dominated, with sulphate domination of anions. The river is contaminated by phenols, oil products, heavy metals, pesticides and nitrogen compounds.

In the past the Amu-Darya played an important role in maintaining fish stocks of the Aral Sea. Its floodplains and delta with its lakes have created favourable conditions for natural reproduction of the major economic fish such as bream, carp and roach. In the Amu-Darya and Syr-Darya rivers the migratory Aral barbel (Barbus brachycephalus) and Aral sturgeon which were feeding in the sea, migrated for spawning into rivers to a distance of more than 1 000 km.

Regulation of the Amu-Darya, manipulation of the flow for irrigated agriculture, and the introduction of Far Eastern fish (especially Chinese carps) in the 1960s led to radical changes in the river biota. Some fish species, whose life cycle was dependent on the river delta, almost disappeared. The gravity of the problem can be seen from the fact that out of 9 fish species listed in the USSR book of endangered species (Anon, 1984) five species - Pseudoscaphirhynchus fedtschenkoi, Ps. hermani, Ps. kaufmanni, Aral trout (Salmo trutta aralensis), pike asp (Aspiolucius esocinus) come from the Aral Sea basin. The Red books of Uzbekistan, Kazakhstan, Turkmenistan and Tajikistan include the same species plus Acipenser nudiventris and Barbus brachycephalus.

Not long ago the Aral Sea catchment rivers harboured 43 fish species (Kamilov, 1973). With the introduction of Chinese carps into the Central Asian water bodies the number of fish species increased to 51 (Amanov, 1985). By the end of the 1980s the major changes in fish species composition and abundance took place in the lower Amu-Darya (Pavlovskaya and Zholdasova, 1991). They recorded only 22 species, which is less than half of the total number of species known from there at the beginning of the 1980s. Among them were eight species introduced from the Far East and these species now dominate the river fauna. Silver carp Hypophthalmichthys molitrix now dominates the pelagic fry stage where it forms about 85-90% of the total spawn, while that of the Aral barbel decreased to 0,04% as against 80% of the total in the 1960s (Pavlovskaya, 1982).

The number of riverine fish species declined and the distribution of Pseudoscaphirhynchus kaufmanni and Aspiolucius esocinus became narrower. Their lower distribution boundary is now by 200 km and 600 km respectively further upstream than before. The Aral sturgeon and the spade fish completely disappeared. It is thought that the main reason for their disappearance is the change in water chemical composition. The migratory stocks of Aral barbel disappeared, but a strictly riverine stock exists in the upper part of the lowland course of the Amu-Darya (Pavlovskaya and Zholdasova, 1991).

Downstream of the Takhia-Tash dam near Nukus, up to the Aral Sea, the Amu-Darya discharge depends from the discharge from the dam. Before reaching the Aral Sea the river is blocked by a dyke situated 80 km from the former Aral Sea boundary. For the last 20 years this dam has made it possible for the Amu-Darya water to be used for feeding into the delta lake system and to the former Aral Sea bays Sarybas and Muinak. This makes possible some fishery in these waters, and to maintain the pastures in the delta. The original fish fauna in the delta lakes has been largely replaced by the introduced silver carp, grass carp, snakehead, goldfish, common carp, and pikeperch.

Fishing on the Amu-Darya is forbidden. The fishery is allowed only in the Tuyamuyun reservoir. There is widespread poaching, especially downstream from the dam, which has a major impact on fish stocks. The reservoir fishery is on a low-scale and has considerable potential for further development.

One of the serious problems facing the fish is the passive transport of the young from the river into irrigation systems. About 90% of the drifting young fish enter irrigation canals and perish on the irrigated fields (Pavlovskaya, 1982). Virtually none of the Amu-Darya irrigation uptakes has a fish protecting device. Those installed in the 1970s turned out to be ineffective. The other serious problem is the preservation of the rare fish species which are disappearing from the modified water bodies. There is need to approach this problem at a state level. Clear guidelines are needed for intersectoral collaboration which would allow harmonization of water quality and quantity demands among the users.

After the Aral Sea fishery ceased to exist the fishery activities moved to lakes and reservoirs. Due to the decrease or complete cessation of the Amu-Darya discharge into its delta major changes have taken place in the location and size of the delta lakes. Due to the water supply interruption to floodplains and delta lakes, lasting for many years, many natural water bodies of the lower Amu-Darya disappeared or became greatly reduced in size, e.g., Sudochie, Eastern Karateren and Dautkul. A new reservoir (Mezhdurechen) was formed by flooding several lakes. Most of the existing lakes began to be fed by collectors bringing drainage water, but completely new lakes such as Ayazkala lake system, Akhchakul, Sarykamysh entirely based on drainage water, also formed in suitable depressions. All water bodies are considered to have some fisheries potential. The present total area of water bodies of the lower Amu-Darya, with the exception of the Aral Sea and Sarykamysh, is estimated at 80 000 ha.

The irrigated agriculture with the ever increasing drainage discharges turned out to be a major factor influencing the environment, including natural waters. At the end of the 1980s, the volume of the collector-drainage water discharge in the Aral Sea basin exceeded 33 km³/y (Table 1). This represented 60% of the long-term mean average discharge of the Amu-Darya and Syr-Darya into the Aral Sea prior to the 1960s. About 17 km³ of drainage waters came from the Amu-Darya basin (including the Karakum canal)

and 13 km³ from the Syr-Darya basin. Three km³ of drainage waters came from other rivers of the Aral Sea basin, mainly Zarafshan and Chu. The average salinity of drainage waters in different irrigated areas of the basin ranged from 1.0 to 14.2 g/l (Chembarisov, 1990).

The great proportion of the drainage waters (more than 20 km³) is returned to rivers and influences their water chemical composition, as well as leading to an increase in their salinity. About 10 km³ of drainage waters enter the Amu-Darya, and 10 to 13 km³ are discharged into depressions. In such depressions over a relatively short period of time appeared a great number of small and large water bodies which increased the total number of lakes in the area, especially in the lower reaches of Amu-Darya and Syr-Darya as documented for example, by remote sensing.

The distribution by number and area of the water bodies receiving drainage is shown in Table 2. More than one-third of such water bodies are situated in the Syr-Darya River Basin and represent 32% of the total surface area. The largest amongst them is the Arnasai lake system (1 865 km²).

About 24% of the water bodies with an area of 52% of the total are concentrated in the Amu-Darya basin. This incudes the biggest depression lake - the Sarykamysh, which now covers more than 3 000 km². The Sarykamysh and the Arnasai lake system together make about 70% of the total water surface area of water bodies established from or receiving drainage waters. Details are given in Table 3.

Most of the water bodies have a low to medium productivity level. They are mostly shallow, of an average depth of 2-4 m, quick to warm up, rich in bottom plants detritus and aquatic macrophytes, with water of alkaline character and no oxygen deficit. The water is usually saline, dominated by sulphates or sodium chlorides. The waters are classified as very hard (11-130 mg eq/l) except a few lakes fed directly by the river, which have water hardness of 10 mg eq/l. The concentration of calcium and magnesium usually exceeds the maximum permissible concentration recommended for fishery water bodies. Concentrations of nutrients, i.e. nitrogen and phosphorus depend on the season, irrigated area, cultivated crops etc. and they also may exceed the maximum permissible concentration, although mostly staying within the limits of the health standards for open water bodies. Only those water bodies directly connected with and supplied by water from the Amu-Darya, such as Dautul reservoir, have good water quality. Planktonic algae, though rich in species, have a low biomass of 0.78-4.15 g/m³ (Babanazarova, 1992). Zooplankton in the lakes is represented mainly by Cladocera and Copepoda and its biomass does not exceed 2 g/m³. The biomass of zoobenthos is also rather low and rarely exceeds 2-3 g/m². The low zooplankton and zoobenthos production is considered as one of the factors limiting the fish production of these lakes.

The profound impact of river regulation on natural lakes is best seen from the changes in fish species composition and fish catch.

The total fish catches in the lower Amu-Darya water bodies have been steadily declining from 7 000 - 8 000 t in the early 1970s to 1 000 to 3 000 t in the early 1990s (Fig. 4). Regarding the individual species, of the 29 indigenous species only half can still maintain self-propagating populations. Some species, e.g. dace, Leuciscus idus oxianus and perch, Perca fluviatilis, have disappeared or are at the edge of disappearance. Ten species were introduced from the Far East, and among them snakehead, silver carp, grass carp and some incidentally introduced fish species such as goby Rhinogobius and sawbelly Hemiculter which came with them, are now common. In many water bodies they ousted the local fish (Guseva and Zholdasova, 1986, Zholdasova and Guseva, 1987) and in some they took the dominant position. Introductions in the Aral Sea catchment water bodies, which took place from 1927 until 1971, made a major impact on the biota of the whole basin, leading to changes in the biota but also in fish production.

Fishery researchers have monitored the impact of drainage water discharges on fish species composition, but also changes in fish morphology, rate of growth, spawning, reproduction pattern, feeding and fish diseases, in the increasingly more hostile aquatic environment. Valuable fish species have been gradually replaced by low-value small-sized species with a short life cycle. Such changes in fish stocks have their impact on fisheries. The present fish yield in most water bodies reaches 10-15 kg/ha/y only.

TABLE 1. Drainage water discharge in the Aral Sea Basin (Anon., 1991a)

TABLE 2. Water bodies in the Aral Sea Basin receiving drainage water (Anon., 1991a)

TABLE 3. Characteristics of selected large water bodies receiving drainage waters

(Anon., 1991a, and author's data)

1 Mean salinity

Among the water bodies receiving drainage discharge from irrigated fields, Lake Sarykamysh attracts considerable attention from researchers and fishery experts. The large lake is shared by Turkmenistan and Karakalpakstan. It was established in 1963 in a desert depression by discharged drainage waters from irrigated lands of the left bank of the Amu-Darya. Since that time, it has continued to grow. In Central Asia and Kazakhstan it is now fourth in size after the Aral Sea, Balkhash and Issyk-Kul. Monitoring of the changes of water quality and its biota provides a unique opportunity to follow the dynamics of this large water body. Many scientists consider the ongoing research on the Sarykamysh as a model of holistic investigations and a pilot study in fishery management of a lake formed from drainage water (Anon., 1991a, Pavlovskaya, 1990).

At present the lake contains about 27 km³ of water with a salinity of 12-14 g/l. Each year it receives about 4.5 km³ of drainage water of 4.7 g/l salinity. The annual dissolved salt transport into the lake ranges between 14-22.5 million tons. The lake water has optimal dissolved oxygen concentrations for fish, a moderate macrophyte community, and a BOD₅ of 1.5-2.0 mg 0₂/l. There is a high concentration of organochlorine pesticides. The algal productivity is moderate but that of zooplankton and zoobenthos is high. The lake is classified as a mesotrophic to eutrophic type (Pavlovskaya, 1990).

The lake fish fauna is formed from fish species which entered it from irrigation systems and from the Amu-Darya. It includes indigenous species from the Aralo-Amu-Darya basin and the Far Eastern species now present in most water bodies of Central Asia. The Far Eastern species (grass carp, silver carp, bighead carp) started as larvae and fingerlings in Sarykamysh during 1969-1974 although with poor results. In total, 36 fish species were identified from the lake, but only 13 of them became well established to support fishery. These are the indigenous valuable fish: eastern bream (Abramis brama), Caspian asp (Aspius aspius), Aral barbel (Barbus brachycephalus), Aral shemaya (Chalcalburnus chalcoides), common carp (Cyprinus carpio), sabrefish (Pelecus cultratus), roach (Rutilus rutilus), wels (Silurus glanis), pikeperch (Schizostedion lucioperca), which are used to existing in saline water and are semi-migratory or migratory. The incidentally introduced and now common fish Rhinogobius is considered a low-value fish (Pavlovskaya and Salnikov, 1990).

All economic fish species reach a large size, have a fast growth rate and a high fecundity. Nevertheless the fish yield of the lake is a modest 13 kg/ha. It has been calculated that the mean zooplankton biomass of 5.4 g/m³ and that of zoobenthos (40 g/m²) could support a much higher fish production of perhaps up to 200 kg/ha. The main reasons for the low fish production are the poor spawning results which are the result of high salinity of the lake, and poor connections with the Amu-Darya which make fresh immigration of fish largely impossible. All fish spawn in the area of the drainage discharge into the lake where the salinity is only about 4 g/l, i.e. a third of that in the rest of the lake. The intensive fishing pressure in the early 1980s led to the decrease in fish stocks and also contributed to changes in catch composition (Fig. 5).

Fishery started in 1966 in the Turkmenistan sector of Sarykamysh. Karakalpakstan started fishing the lake only in 1980 and stopped fishing in 1988 as it turned out to be economically non-profitable for reasons of the long distance between the water body and the place of fish processing, and because of the low fish quality. The Karakalpak fishing areas are situated in the north where water salinity is higher than in the south. In the northern part of the lake dominate the small razorfish, roach and bream, while the south

has the larger carp, Aral barbel, wels. The highest fish catches were obtained during 1981-1985 (2 119 - 2 942 t). Between 1988 and 1992 the fish catch decreased from 1 101 to 335 tons.

The fishing effort in the Sarykamysh has routinely exceeded a sustainable level. Recommendations from fishery scientists have been ignored and as a reason for this was given that the lake has only a temporary character. Mainly valuable fish such as Aral barbel and common carp, were targeted first which led to their decrease. The development of the lake fish fauna followed similar tendencies as in other new artificial water bodies: decline of the valuable fish Barbus brachycephalus, Cyprinus carpio, Silurus glanis and the increase of low value fish Abramis brama, Pelecus cultratus and the predator Stizostedion lucioperca. The replacement of the dominant species has gone parallel with the decrease in the valuable fish (Fig. 5).

In the future, irrespective of the development of the aquatic environment in irrigation systems and in the Amu-Darya, major changes in fish stocks of Lake Sarykamysh will be determined by the gradual increase in water salinity, typical of stagnant waters of the arid zone. Monitoring of water for concentrations of mineral and toxic substances has shown that Sarykamysh is going through a period of a rapid salinity increase which is leading to the deterioration of its whole ecosystem (Anon, 1991a). By 1995 the mean salinity is expected to reach 16 to 18 g/l. Such salinity will place a serious constraint on freshwater fish stocks which will further decline and some species may disappear completely. The absence of euryhaline fish species means that eventually the lake will be without fish. According to Yudovich and Shaporenko (1987) by 1995 the fish catch is expected to be only 340 t, and by the year 2 000 no fishery will exist.

The fate of Lake Sarykamysh will depend on the future development of the lower Amu-Darya, on measures taken for the restoration of the Aral Sea, and on other human activities in the area. The Sarykamysh example shows that fisheries in water bodies receiving only drainage and wash water from irrigated fields could be of only a temporary nature. The gradual increase in water salinity reduces the biodiversity of aquatic organisms including fish, with the valuable fish species gradually disappearing. This is further complicated by the high concentration of pesticides and heavy metals. The fish from Lake Sarykamysh exceed permissible levels of pesticides for food products. In the 1970s fish tissues contained 0.78 mg/kg (Anon., 1991a), in the 1980s, 0.66 mg/kg of pesticides. Lowering the level of chemical pollution could be the first step in rehabilitation of fish stocks, but to arrest the salinity increase would require that sufficient amount of low-salinity river water is supplied to such water bodies on a continuing basis.

The Aral Sea Basin is a major receiver of chemicals used for plant protection. Chemicals are used for seed preparation, for sowing, as pesticides and weedicides, for cotton defoliation at cotton picking time. The drainage leaving the fields contains about 3% of defoliants, 2-3% of the used pesticides, 10-15% of nutrients (Dukhovny, 1984). The presence of chemicals in water makes it a poor environment for fish. The chemical pollution of the surface waters is a serious problem of the region. In Karakalpakstan, situated in the lower Amu-Darya, pollution of waters is the highest. The concentration of pollutants in water results not only from the inflowing polluted drainage water to the delta, but also from the heavy use of chemicals in the Republic itself where agro-chemical application in agriculture ranges from 20 to 54 kg/ha. The agro-chemicals are then passed on via drainage systems into rivers and lakes where they accumulate.

In fish the maximal content of hexachlorane was 2.5 mg/kg; the concentration of DDT and its metabolites was 6.4 mg/kg. Benthos-feeding fish in many water bodies suffer from cirrhosis of liver and disorders of fat metabolism. Organichlorine pesticide concentrations of 0.0211-0.0059 mg/kg lead to the death of fish eggs in females, prevent hatching of eggs or the hatchlings are deformed. During the 1980s several cases of pesticide poisoning fish were recorded from water bodies of Uzbekistan and Karakalpakstan. The mass mortality of silver carp in 1990 and in 1991 in the Tuyamuyun reservoir on the Lower Amu-Darya caused a major concern (Zholdasova, Pavlovskaya and Lyubimova, 1991).

The one-sided use of water resources for irrigated agriculture has caused considerable damage to fish stocks and to the fishery of Karakalpakstan. The chain of events started with the decline and eventually the total halt of the Aral fishery, which has been accompanied and later on followed by the decline of fishery in water bodies receiving drainage waters.

Thus, during the last 30 years the preference in the use of the Amu-Darya waters was given to irrigation needs of agriculture but very little to fisheries needs. It was believed that the Aral Sea will remain an important source of freshwater fish for the foreseeable future and that the water diversion for irrigation cannot influence this. Some warnings on the potential negative consequences of the irrigation were already received in 1940-1950s (Anon., 1950; Anon., 1964). Fisheries managers took some measures and a number of hatcheries and fish farms were constructed in the lower reaches of the Amu-Darya and Syr-Darya. During the last 20 years Uzbekistan and Karakalpakstan prepared programmes for modernization of fish production and fisheries under new conditions created by the impact of water resources manipulation for irrigated agriculture. Two fish farms were constructed: one in 1974 in Nukus, another in 1979 in Muinak. The first one was built for breeding sturgeon and the Aral barbel, while the Muinak farm was to breed common carp and Chinese carps and to produce stocking material for lakes of the Amu-Darya delta.

The Nukus fish farm never bred the migratory fish species, as originally intended; instead it has been used for production of cyprinid fish for stocking lakes. The farm has also carried out capture fishing in lakes. The Muinak fish farm is the only fishery enterprise in the country which produces both stocking material and fish of marketing size. It has a production capacity of 50 million fish larvae of the common and Chinese carps, with 80% survival to fingerling stage for stocking. It also produces two year-old fish for the canning industry.

The fish processing industry of Karakalpakstan is based in Muinak on the shore of the drying Aral Sea. It consists of the Muinak fish farm, the fish cannery and three fish factories which are engaged in fishing, salting and smoking of fish and supplying the cannery. Four other fishing units under one management are also catching fish. The fishery employs about 200 people. The cannery, built in 1936, is in great need of reconstruction, the cost of which is estimated at US$ 3 million, which at present the Government of Uzbekistan is unable to provide. Besides the reconstruction the plant also needs a regular supply of fresh fish, tin and some other material for its production. Lakes which are now the main source of fresh fish at present cannot supply the plant with enough fish because of their low fish production. For almost 20 years the factory was receiving oceanic fish such as horse mackerel, Atlantic mackerel and sardines from Russia and Baltic states, but the supply has become irregular as a result of the weakening of economic ties between the countries of the former Soviet Union. The Muinak Fish Farm also cannot meet the production needs of the fish cannery due to the shortage of the Amu-Darya water. This shortage results in only 20-35% use of the hatchery and ponds. The fish farm also needs considerable rehabilitation. At present it is able to produce from its ponds only 350 t of fish.

The future of the fishery in the lower Amu-Darya depends much on solving the problem of the Aral Sea and its catchment. Only implementation of a water resource rehabilitation programme could lead to the rehabilitation of fish stocks and fisheries. Some of the measures such as re-distribution of the water resources and improvement of water quality, can be achieved only as a result of international collaboration of all countries of the Aral Sea basin, i.e. Karakalpakstan, Uzbekistan, Turkmenistan, Kyrgyzstan, Kazakhstan and Tajikistan.

To maintain the fishery of the lower Amu-Darya and its associated water bodies will require:

1. To recognize the importance of Karakalpakstan fishery and the need for its rehabilitation and adaptation to the new conditions as given by the modification of water bodies through requirements of the irrigated agriculture. This would be possible only through major capital investment.

2. To strengthen the Government policy of nature protection, especially through addressing the problem of drainage water discharge into the Amu-Darya and to enforce the existing water quality and environment protection laws and regulations.

3. To design and to construct fish hatcheries and fish farms for stocking natural water bodies and for fish processing; to establish fish feed mills and production of fish food organisms; to train specialists.

4. To initiate fish breeding of rare and disappearing species of the Aral fish fauna with the aim of rehabilitating their stocks.

Implementation of this programme will require much effort and it may require assistance of international organizations such as FAO.

REFERENCES (all references in Russian, where not otherwise stated)

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