1/ Abdullaev and Urchinov, 1989

1/ without Karakalpakstan

TABLE 12. Uzbekistan lakes of groups 2 and 3

TABLE 13. Grouping of Uzbekistan reservoirs by size and river basin

Running waters of the Khorezm region are inhabited by the rheofilic fish Amu-Darya stone loach, Aral barbel, shovelnose, Aral asp, razorfish, pikeperch. Those with preference for still waters are Aral bream, crucian carp, gobies, rudd, white-eye, pike, roach, ide. The majority of commercial fish species mature in the second or third year (bream, wels, common carp, white-eye, roach, crucian carp, razorfish), and the low-value Turkestan gudgeon, striped bystranka, spiny bitterling, golden spiny loach, stone morokos which lay eggs during the first and second year. Aral asp and Turkestan barbel mature at the age of 4-6 years. Mature males are usually smaller than mature females.

Spawning of the riverine fish takes place during spring and summer. Asp, roach, pikeperch and white-eye spawn over a period of one week to one month, with the whole batch of eggs being released at once. The spawning period of the other species (serial spawners) may extend over 2-3 months.

Starting in mid-April large quantities of fish larvae and some juvenile pikeperch - up to 1.5 million within 24 hours - enter irrigation canals (Table 14). The larvae and juveniles are carried by the current. In May small pikeperch dominate in irrigation uptakes, but the number of fish is lower than in April. On average 200 000 juveniles and larvae enter the irrigation system every 24 hours through the two canals, starting from the pumping station. It is estimated that in May the pumping station lifts 27 million cubic metres of water from the Syr-Darya, and with it 4.5 to 5 million juvenile fish which end on irrigated fields (Table 14). During June-August the bulk of fish pumped into the canals are juveniles, but there are still some fish larvae as well.

TABLE 14. Juvenile fish incidentally pumped out from the Syr-Darya with irrigation water

In spring, when river water is murky and there is a strong current, the young fish cannot orientate visually and cannot resist the current and therefore enter the pumps. In summer the juveniles are bigger and more capable of resisting the current and in the less turbid water they can avoid the pumps.

Aquatic macrophytes represent a major problem for irrigation canals. This problem has been handled in the Karakum Canal by introducing grass carp. This canal, which branches off the Amu-Darya River, and its lateral lakes, has in the past experienced growth of aquatic plants on a large scale. To sort out the problem, grass carp was introduced in 1958 and released in large numbers in 1960 and 1961. By the mid-1960s, large-scale natural reproduction of grass carp took place and within a few years most of the aquatic macrophytes disappeared. Some problems, however, remained. Selective feeding of the grass carp led to succession in macrophytes, with Myriophyllum spicatum being replaced by Ranunculus, which is considered toxic to grass carp. Charyev (1984) who summarized the experience with the introduced Chinese carps into the Karakum Canal, emphasized the need to protect the higher aquatic vegetation, particularly in cases where macrophytes represent spawning substrate for other fish, such as common carp. The combination of three Chinese carps, viz. grass, silver and bighead, has been considered very suitable for maintaining good water quality, and at the same time the three carp species constitute 75 to 80 percent of the total catch from the canal and its associated water bodies.

Grass carp and silver carp stocks in reservoirs, lakes and irrigation canals depend on a number of variables, such as predatory fish, size of fingerlings of Chinese carps used for stocking, and the character of the water body itself. Good results are obtained if 2-year-old fish are stocked but hydrological parameters such as width, depth, transect of the canal, current velocity in it are also of importance and determine what size of fish to be stocked and when. The density of stocking grass carp will depend on the quantity of aquatic plants present in the irrigation system. Large canals should be stocked with 2-3 year old carps, small canals and collectors with 1-2 year-old. Large canals should be stocked in autumn, small canals and collectors in early spring. During the first year after stocking there is usually little effect on aquatic plants, but results become clearly visible during the second and third years.

Irrigation of the Hungry Steppe soils required construction of many collector canals, of a total length of over 1 000 km. The function of these canals was to collect the residual water from irrigated fields. The water entering collectors from fields has an elevated salinity and this encourages the growth of aquatic plants. Small collectors will overgrow with aquatic plants already during the first year. The first to appear are usually submersed filamentous algae, Potamogeton pectinatus and P. crispus, Zanichellia sp. and in some canals also Naias maritima and Ruppia maritima. Later on sixty percent of these are replaced by the reeds Phragmites communis and Typha angustifolia.

Much of the drainage and collector water is reused. This leads to a gradual increase in water salinity and to salinization of irrigated land. From the annual volume of 19 to 21 km³ of drainage water in the Amu-Darya river basin, 9.7 km³ is returned back to the river. Over the last 30 years water salinity in the lower Amu-Darya has increased to 3 g/l. Such salinity causes problems both in the irrigated fields and in water bodies receiving drainage water.

5.2 Floodplain lakes

The lower Amu-Darya lakes and lakes in the Khorezm region of Uzbekistan are fed by drainage and ground water. The lakes of the Khorezm oasis are of three types: those fed by the Amu-Darya water through irrigation systems; those which do not receive the Amu-Darya water but are connected through collectors with other lakes, and those which partially or completely dry out during summer. The chemical composition of water differs. Water salinity ranges from 1 044 to 3 040 mg/l. Those floodplain lakes situated many kilometres from a river, with river water reaching them only in autumn and winter, experience a drop in water levels in spring and summer. This may be accompanied by an increase in water salinity, which negatively affects especially the young of common carp and bream. The pH in floodplain lakes ranges from 7.2 to 8.2, dissolved oxygen concentration from 8.2 to 17.7 mg/l, which corresponds to 90.6 to 198.4 % saturation. In several lakes (Abulkul, Khodzhakulgan and Tokizchokur) the dissolved oxygen concentration at the bottom declines to only 55% saturation in summer. The lakes' ionic composition is dominated by sodium chlorides. They are rich in plyto- and zooplankton. Mysids and freshwater prawns entered the lakes from the Amu-Darya and Syr-Darya and are also consumed by most fish species.

Floodplain lakes of the Amu-Darya in Uzbekistan still have good spawning and feeding conditions for the local fish. At present some 50 species of fish are found in these lakes, and 20 species are of economic importance. While common carp, pike and wels are heavily fished, the low-value species such as roach, dwarf common carp, goldfish, and perch are neglected. As a result, stocks of low-value fish are high. Fish yields in lakes average about 15 kg/ha. Currently, attention is being paid to increasing the fish production of Lake Tuzgan (Dzhizak region) and Ulli-Sharkul (Khorezm region), which cover some 32 000 ha. Management measures proposed are stocking of mysids and introduction of gammarids from the River Don delta and from Mingechaur reservoir. Another proposed measure is to develop combined fish stocks of common, grass and silver carps.

Enhancement of lake and reservoir fish production has become a priority with the collapse of the Aral Sea fishery. In the Khorezm region, situated in the Amu-Darya delta and one of the oldest agricultural areas in the world, there are more than 100 water bodies suitable for fisheries. Since 1974 Khorezm Fish Farm, with 900 ha of ponds, has been producing 2 600 - 2 900 kg/ha of fish. The total fish pond harvest is about 20 000 t/y. The pond area will be expanded to 1 500 ha. Fisheries managers hope also to harvest a total of 5 000 t from open waters of this region. and there are plans to convert lakes with low fish production into managed fish-producing water bodies.

5.3 Reservoirs

Of the 80 species listed for Uzbekistan reservoirs, twenty have economic importance. A fishery exists on seven reservoirs. The catches change from year to year. In 1970 the total catch from reservoirs was 328.8 t, in 1975-1979 it ranged between 100 and 200t. Reservoir fisheries management has focused on the following:

- introduction of new fish species and fish food organisms

- management of spawning sites, fish protection, improvement of the efficiency of fishing methods

- intensification of fish production in separated or isolated parts of reservoirs

- fish production in the littoral zone

- pond and cage culture.

Reservoirs Kattakurgan, Kuyumazar, Tudakul and Chimkurgan, which have low or no stocks of introduced fish, have also very low yields. Common carp, which forms 15 to 20% of all fish stocks, is the most important economic fish species.

Reservoirs in the semi-desert or desert areas, viz. Farkhad, Kairakkum, Kattakurgan, Kuyumazar, Tudakul, Chimkurgan and Uchkyzyl have a relatively low primary and secondary production and therefore poor fish food resources. In spite of that, the introduced Chinese carps which feed on macrophytes and plankton, became well established in some of these reservoirs (e.g. Chimkurgan). This shows that such reservoirs have good fisheries potential, and that the estimate of natural fish food production should not be based on standing crop but on turnover rate, which, due to the high water temperature and insulation is believed to be high. There is a need for fundamental studies on the primary and secondary productivity of reservoirs, as well as on biology and fish dynamics, both for the native and introduced fish species.

During the 1950s to 1980s the following fish species were released in Uzbekistan reservoirs: goldfish, Aral bream, pikeperch, silver carp, grass carp, bighead carp and some other species of fishery importance. Together with them, 15 species of low-value fish were also incidentally introduced. While the first group of fish was becoming established, the fish of the second group, due to their high adaptability to new conditions, quickly spread though the water bodies of Uzbekistan. As a result, the original fish fauna composition has changed considerably. Some valuable fish species such as khramulya, Turkestan barbel and shemaya, as well as the less valuable Zarafshan dace, ostroluchka, gudgeon, riffle minnow have become rare.

The proposed management measures include stocking of Chinese carps, establishment of artificial spawning substrates, and expanding closed seasons and closed areas. Regular stocking of the common carp and Chinese carps should increase the reservoir fish yield to 40-50 kg/ha, resulting in an annual reservoir fish catch of 1 600 to 2 000 t of fish.

Establishment of reservoirs has had a positive impact on the growth rate of the wild form of common carp. In the Amu-Darya reservoirs Uchkyzyl, Dagrez, Yuzhnosurkhan and Chimkurgan a two year-old common carp ranges between 14.9 and 16.8 cm length, while in the rivers Kafirchirgan, Surkhan-Darya and Amu-Darya (region Termez-Aivaj) the length is only 10.5-12.1 cm. A four-year old carp in Surkhan-Darya and Amu-Darya is 21.3-22.3 cm long, in reservoirs 25.3-28.1 cm. The fast growth rate in reservoirs is noticeable and this is surprising as the carp there feeds on plant detritus. In reservoirs, common carp faces the problem of finding suitable spawning sites, as a rapid drop in water level due to irrigation demands is common. As a result, fertilized eggs of carp, bream, crucian carp and wels usually die. Nevertheless a large fishery development potential exists in Uzbekistan reservoirs and can be realized by regular stocking of hatchery-raised fingerlings. Further intensification is possible through developing semi-intensive fish culture in cages, which could be made largely independent of reservoir water level fluctuation. Induced breeding could be practised on fish other than Chinese carps, such as Turkestan bream and Aral asp, khramulya and snowtrout which require river currents and are migratory. Both conditions are no longer available to them.

Current fish yields of Uzbekistan reservoirs range between 7 and 30 kg/ha and this is considered to be low. At present any increase in catch is achieved through an increase in fishing pressure.

Lakes, as well as reservoirs, have major importance for fish and fisheries. Due to the high silt load, turbidity and fast current, as well as rapid changes in discharge rates, the rivers Zarafshan, Surkhan-Darya and Kashka-Darya have little fishery importance. In summer Kashka-Darya completely dries out while Surkhan-Darya and Zarafshan carry only a small amount of water.

Factors that determine the current low fish production of Uzbekistan reservoirs and other water bodies are still not clear enough to allow formulation of sound management strategies for a steady increase in fish yields. It is probable that each reservoir and lake may require a specific approach. The management measures need to address protection of the existing fishery resources, especially of the riverine fish of the Syr-Darya, Amu-Darya and Zarafshan, current levels of fishing pressure, ways of increasing fish stocks in the individual reservoirs and floodplain lakes. Special attention needs to be paid to small lakes and the potential for converting them into semi-intensive well managed fisheries bodies.

Formation of reservoirs has caused major changes in the riverine fish stocks, and fish species requiring water current (rheophilic fish) have gradually declined. Only those species of backwaters continue to be common. Each reservoir has developed its specific features, determined especially by its morphometry and altitude in which it is situated. Lowland reservoirs, due to their shallowness and water temperatures, have become normally more productive than those situated higher upstream.

Table 15 shows that the highest number of economically important fish species is present in the Syr-Darya basin, followed by Amu-Darya, Zarafshan and Kashka-Darya. Sixteen economic species (equal to 19.2% of the total) have been introduced into the Syr-Darya. In the Zarafshan, the introduced fish species of economic importance represent 20.5%.

In 21 water bodies out of 28 (Table 16), the number of fish species of economic importance in reservoirs and lakes of the four river basins of Uzbekistan range between 44 and 76%. The number of predators ranges from 0 to 5, with a mean predator/non-predator ratio of 8:1 for the total of 28 water bodies.

While lakes have been fished for many years, fishing in reservoirs started with their formation, i.e. largely during the second half of this century. Fishing rights are given to fishing companies and can change from year to year. This contributes to the poor quality of statistical data. This can be seen from the difference between the two sets of data available for some water bodies and collected by two different fishing companies (Tables 17 and 18). Information on catches of individual fish species is not available. Lowland reservoirs usually contain more commercial fish species than foothill and mountain reservoirs and lakes.

The major commercial fish are common carp, Aral white-eye (Abramis sapa), silver carp, bighead carp, pikeperch, grass carp, pike asp, Aral barbel, goldfish and wels. The formation of fish stocks in new reservoirs was influenced by management including introduction of exotic fish species and their food organisms, and by stocking (Table 15). The management has yielded variable results. During the first years the new reservoirs contained less fish than later on when fish started immigrating into reservoirs through the new canals connecting them with other rivers, and more fish species were introduced and stocked. The final result is that the fish fauna in each reservoir has a different set-up, as can be seen for example from the number of predatory and non-predatory fish (Table 16). Nevertheless, the water bodies of Uzbekistan represent an important fish production base. It is well understood that this resource needs to be rationally exploited and managed and that irrigation reservoirs and water bodies resulting from irrigation practices can be further developed for fisheries to maximize the benefits. This includes the production of fish of high quality for which there is a great demand.

TABLE 15. Fish species composition by river basin (Uzbekistan)

TABLE 16. Fish species composition in the individual water bodies of Uzbekistan

TABLE 17. Fish catches (tons) from selected reservoirs of Uzbekistan (Source: fishing company Uzryba)

TABLE 18. Fish catches (tons) from water bodies of Uzbekistan (Source: fishing company Uzbekrybvoda)

During 1990-1993 the fishery was targeting predominantly wild stocks. There still exists a number of water bodies which are not fished, and for others there are no reliable fish catch statistics which would allow us to obtain a better picture on fish species and fish stock densities, and to estimate the sustainable fish production of such water bodies. An estimate of the total fish production from all inland water bodies of Uzbekistan, as given in Table 19, is based on fishery statistics of two fishing companies (Uzryba and Uzbekrybvoda), on information provided by the Government Control Unit of the Government Commission for Nature and on fisheries literature. The statistics show a gradual increase in fish catches over the period 1981-1991. During the first three years, the collapse of the Aral Sea fishery contributed to the decline in fish catches between 1982 and 1983 but afterwards the catches have maintained a range between approximately 7 000 and 8 000 t, with the exception of 1990, when less than 6 000 t was captured. Fish came mostly from lakes, which yielded ten times more fish in 1991 than reservoirs. River fish catch has widely fluctuated, with little fish captured in 1991. At present it is difficult to speculate on the reasons behind this sudden collapse in riverine fisheries.

TABLE 19. Fish catches (tons) - Uzbekistan

It is believed that there is much scope for increasing the low fish catches from reservoirs, if suitable management measures are applied. Today's low fish production is considered to be the result of several factors:

The fishery managers need to target the above problems either individually or in totality, if better results are to be achieved.

Specific fishery management measures for each river basin have been proposed with the objective of optimizing the yields. For Ferghana Valley water bodies, the following mix of species are recommended: (i) those reproducing under the existing conditions (Group 1), i.e. snowtrout (Schizothorax intermedius), Barbus capito, wels, Aral asp, (ii) those to be stocked annually (Group 2), i.e. Coregonus peled, silver carp (as phytoplankton feeder), and common carp (benthos feeder).

For the water bodies of the Zarafshan basin. Group 1: white eye (Barbus capito), Herat khramulya (Varicorhynchus heratensis), goldfish. Group 2: common carp, silver carp, grass carp, Aral asp and pikeperch (the last two are piscivore).

For the first and second group of reservoirs (see Table 11) of the Kashka-Darya basin.

Group 1: snowtrout. Group 2: silver carp, common carp, grass carp and pikeperch.

For reservoirs of the Surkhan-Darya basin. Group 1: white eye (Barbus capito), khramulya, pike perch and wels. Group 2: bighead, common carp.

For all lowland and some foothill reservoirs the species of major economic importance are: common carp, (Barbus capito), khramulya. In some years conditions for their reproduction are very poor and without stocking the production would be extremely low. There is enough potential in the existing fish hatcheries to produce a sufficient amount of stocking material. A better organization of commercial and recreational fisheries would also result in higher yields. It is believed that if appropriate management measures are introduced, 4 to 6 times higher yields, i.e. 30 to 40 kg/ha could be achieved.

5. REFERENCES (all in Russian, except where marked)

Abdullaev, M.A., 1969. Biological basis of national reservoir fisheries in the desert zone of Uzbekistan (river basins of the Bukhara and Kashka-Darya regions). Ph.D. thesis, Tashkent

Abdullaev, M.A. and D.U. Urchinov, 1989. Commercial fish in waterbodies of the lower Zarafshan. Publ. FAN AN Uz SSR, Tashkent

Abdullaev, M.A. and D.U. Urchinov, 1989. Economically important fish in water bodies of the lower Zarafshan River. Pub. FAN, Tashkent

Amanov, A.A., 1963. Ichthyofauna of the waterbodies of the Surkhan-Darya River Basin. Doctor's Diss., Frunze

Amanov. A.A., 1985. Fish ecology of water bodies in the south of Uzbekistan and neighbouring republics. Pub. FAN, Tashkent

Baimbetov, A.A. et al., 1975. Taxonomy and biology of pikeperch from Kapchagay Reservoir. Biol.Nauki, Alma-Ata, Kaz GU, Vol. 9

Berg, L.S., 1948-9. Freshwater fish of the USSR and neighbouring countries

Charyev, R., 1984. Some consequences of the introduction and acclimatization of grass carp, Ctenopharyngodon idella (Cyprinidae) in the Kara Kum Canal. J.Ichthyol. 24(3):1-8 (in English)

Dukravets, G.M., 1976. Ichthyofauna of Tilikul lakes. Abstract in: Biological basis of fisheries of Central Asia and Kazakhstan. Balkhash.

Gladkov, N.A., 1934. Fisheries research of lakes Kamyshlybash. Tr.Aral.otd.Inst.Ryb.Khoz., Vol.3.

Kamilov, G.K., 1973. Reservoir fish of Uzbekistan. Publ. FAN, Tashkent.

Khakberdiev, B., 1983. Fish in reservoirs of the Khorezm District. Publ. FAN AN Uz SSR.

Lindberg, G.U., 1955. Quaternary in the light of biogeographic evidence. Publ. AN SSSR, Moscow-Leningrad.

Maksunov, V.A., 1961. Biomorphology of fish of Farkhad Reservoir. Tr.Inst.Zool.Parasit. AN Taj. SSR, vol. 23

Nikitin, A.M., 1987. Lakes of Central Asia. Publ. Gidrometeoizdat, Leningrad

Nikolsky, G.V., 1949. Fish of the Aral Sea, MOIP.

Nikolsky, G.V., 1956. Fish of the Amur Basin. Publ. AN SSSR.

Taubaev, T., 1958. Overgrowing of irrigation canals in Khorezm District, Central Asia. In: Canals of USSR; Publ.Nauchnaya mysl, Kiev.

(The references, as given by the authors, could not be checked against originals. Any errors are regretted)