In northeastern Kazakhstan, there are two zoogeographically distinct coldwater fish faunas: that of the River Ob catchment, including the Altai Mountains drainage of the Irtysh River, and belonging to the circumpolar zoogeographical region; and that of the Asian montane zoogeographical region, including Tien Shan, which has ichthyofauna typical of the landlocked Balkhash basin. Lake Balkhash itself is a low-altitude water body, with a mix of coldwater and temperate water fish stocks. Since the beginning of the 20th century Lake Balkhash fish stocks have been intensively manipulated through transfers of additional fish species from other river basins situated within the ex-Soviet Union. This has led to a rapid sequence of changes in the dominant fish species, with the indigenous fish stocks declining, and introduced species replacing them, but with little change in the total catch. This has shown that the manipulation of lake fish stocks has not been rewarding from an economic point of view. In the Alakol lakes east of Lake Balkhash introductions started in 1930, and resulted in fish stocks now being dominated by the introduced bream and pikeperch. In Lake Markakol in the Altai considerable effort has been put into hatchery production of the indigenous fish lenok (Brachymystax lenok, Salmonidae). However, it is still the wild stocks of this species in the lake which provide eggs for stocking other coldwater lakes. No attempts have been made to develop fish stocks in the mountain rivers of Tien Shan, but rainbow trout was stocked in several mountain lakes. Initially very successful, they soon reached high densities resulting in exhaustion of the natural food leading to cannibalism and appearance of dwarf males, but gradually the stocks reached an equilibrium. The introduced rainbow trout has had a negative impact on native fish, which have been severely depleted through trout predation. The future of rainbow trout is now seen to be the establishment of culture systems with artificial feeding.
While fish stocks in Lake Balkhash (Fig. 1) have been manipulated in order to increase fish production by trans-basin fish introductions since the beginning of this century, the fishery in mountain water bodies of Central Asia and Kazakhstan has concentrated largely on the exploitation of indigenous fish stocks. However, a further increase in yields has been considered possible for some water bodies of the Kazakhstan Altai, Dzhungarskiy Alatau and northern Tien Shan (Fig. 1). These areas have a number of lakes and rivers as yet largely unaffected by human activities, and reservoirs where fish stocks have already been managed in some way. Apart from the intensification of capture fisheries, their coldwaters could be used for semi-intensive culture of market-size fish and/or for the production of stocking material for regular stocking of coldwater bodies. It is known that some of the indigenous fish species have the potential to improve fish yields in the existing water bodies, or to be introduced in fish culture. Further possibility for increasing yields still exists through inter-basin transfers of fish species in selected mountain lakes and reservoirs.
All water bodies in the Altai mountain system belong to the Ob River catchment. The northern slopes of the Altai are drained by the rivers Katun and Biya and their tributaries. The fish fauna of these rivers is related to that of the southern slopes of the Altai and comprises a number of salmonids, coregonids and some cyprinids. The River Black Irtysh in China and Kazakhstan marks the southern border of the Altai Range, separating it from the distant mountains of Central Asia. The fish fauna belongs to the circumpolar zoogeographical region. Rivers draining Tien Shan mountain ranges and southern Dzhungaria (Kazakhstan and China) end in landlocked Lake Balkhash or disappear in a desert. There are marked differences between these two regions: fish of the salmonid family dominate in water bodies of the Altai, while the cyprinid Schizothoracinae prevail in water bodies of the southern Dzhungariya and in Tien Shan. Geographical barriers virtually prevent mixing of the two fish faunas. The two major rivers, Black (Cherny) Irtysh and Ili, the latter originating in Xinjiang Province, China, from where it enters Kazakhstan and passes north of the mountain ranges of Zailiyskiy Alatau of the northern Tien Shan, are separated by such a barrier. The Altai Region has a dense river network, with the rivers having largely stable flow rates. Lake Markakol in Kazakhstan is an Altai lake which has been subject to fish stock management efforts.
The northern Tien Shan mountain system comprises several ranges. The ranges of Zailiyskiy Alatau and Kungey Alatau are parallel with Lake Issyk-kul bordering it in the north. While many streams of the Kungey Alatau run into Issyk-kul, those of Zailiyskiy Alatau mostly enter the River Ili, which itself ends in Lake Balkhash. South of Lake Issyk-kul and in parallel with it, extends the range of Terskey Alatau, and west of Lake Issyk-kul starts Kyrgyzskiy Khrebet. Most streams draining the last mountain range feed into the River Chu, which eventually ends in deserts of Kazakhstan, close to the River Syr Darya. Fish stocks and fisheries in Issyk-kul, in water bodies of the southern Tien Shan, and in the River Chu are dealt with in another paper in this publication (see Savvaitova and Petr).
Rivers of the two most northern ranges of Tien Shan provide vital water supply for Lake Balkhash. The river network is dense, each river having numerous tributaries. There is plenty of underground water which has a constant temperature throughout the year. The water has a high dissolved oxygen content and is low in minerals. A number of mountain lakes in this region resulted from landslides which blocked valleys. Some of the dams formed by landslides are unstable and can be broken through by mud and rock slides, which are quite frequent. This is a constraint hindering the establishment of stable fish stocks and it also prevents the establishment of a salmonid-based fishery. Most mud and rock slides take place in summer and are caused by rain, resulting in a short-lasting but sudden increase in discharges. Such floods rapidly increase the water turbidity and the high concentration of suspended solids may clog fish gills resulting in fish kills.
Lake Balkhash and the Alakol lakes, the latter situated north of Dzhungarskiy Alatau and east of Lake Balkhash, represent isolated drainages. Both lakes are slightly saline. The largest river in the Balkhash system is the Ili. The Ili receives many tributaries from the high mountains of the Zailiyskiy Alatau and Kungey Alatau situated south of it. Some rivers of Dzhungarskiy Alatau situated north of the River Ili drain south into the Ili, while others supply water directly to the Alakol lakes and Lake Balkhash. Karatal, which originates on the western slopes of Dzhungarskiy Alatau, is the second largest river reaching Lake Balkhash. Some of the rivers flowing towards Lake Balkhash reach it only in spring, due to the seasonal fluctuation in discharges and the irrigation demand. The drainage area of Lake Balkhash is geographically separated from that of the Aral Sea, but both water bodies share many common fish species, most of which belong to the Schizothoracinae and Gobiidae.
In the Altai region the fish fauna is dominated by salmonids Hucho taimen, Brachymystax lenok and Thymallus arcticus. In the mountain sections of the River Irtysh fish of the genera Salmo, Salvelinus and Coregonus are present. Damming of the River Irtysh resulted in the formation of Bukhtarminsk reservoir, with Lake Zaysan becoming part of it. When full, this reservoir covers an area of 5500 km2 and between 1980 and 1991 it yielded from 5442 to 8483 t yr-1 of fish (Karpova et al., 1996). In the reservoir bream, with 87% of the total, dominated the catch in 1991, followed by pikeperch, perch and roach.
2.1 Taimen - Hucho taimen is present in all the right-side tributaries of the Irtysh in Kazakhstan and also in the other rivers of the Altai, with the exception of the left-side tributaries of the Irtysh. The fish spawn in May and females lay up to 44,000 eggs. Taimen is a fast growing fish and has a high quality flesh. It is a typical predator, highly prized by anglers. Usually it is processed into a smoked dried product. The red-coloured eggs are considered to have the quality of the red caviar of the Far Eastern salmons. Taimen is not a common fish of the Altai because being a solitary predator it requires a long stretch of river to find sufficient food. Only when spawning do the fish form small shoals. Owing to the low occurrence of this fish, its importance is largely as a sport fish. The major problem of producing stocking material under hatchery conditions is that the taimen broodstock-sized fish weighs more than 10 kg, and it has proved difficult to keep such large fish alive in hatcheries for stripping. At present there exists no reliable methodology for taimen culture.
2.2 Lenok - Brachymystax lenok is a widespread salmonid, present in the upper courses of rivers draining into the Arctic Ocean or into the Pacific. It is also present in coldwater lakes. It appears in long-snout and short-snout forms. Both forms may inhabit the same water body. Lenok may be present in large numbers, which makes it possible to fish it commercially. Lake Markakol, which is situated at an altitude of 1449 m southwest of the Khrebet Yuzhniy Altai in the northeastern Kazakhstan and which covers 450 km2, has the largest lenok fish stocks known for the coldwaters of Asia. In the 19th century annual catches of this fish from Lake Markakol might have reached 1500 t yr-1. Most of the fish were captured in spring when spawning. It is said that during spawning they might have laid perhaps 60 t of eggs. Presently, the fishery captures less than 100 t yr-1.
Lenok seems to be a suitable fish species for introduction to other water bodies in Asia. It spawns in spring for about 3-4 weeks, after the ice cover has melted. The heaviest individuals that spawned already in previous years are the first to spawn, whereas those spawning for the first time (2-3 year-old males, 3-4 year-old females) spawn towards the end of the spawning season. The average number of eggs laid by a female is 2000, but up to 5000 may be laid on a stony bottom. The eggs will hatch in 19-50 days, depending on the water temperature: in 50 days at 4.5oC, in 22-19 days at 7.2-14.8oC. Under experimental conditions lenok spawning was induced by using pituitary injection and it is believed this species could be farmed. However, the low number of eggs per female is a constraint for mass production in farm conditions (Votinov, 1963). Today the common practice is to collect eggs from the wild, i.e. from Lake Markakol, Lake Teletskoe in the Russian Altai on the upper Yenisei River, and from lakes in Mongolia, and hatch and grow them in hatcheries and on fish farms.
The fry starts to feed 12-15 days after hatching. The yolk sac is retained for 20-25 days. The fry is resistant to oxygen deficit: at an incubation temperature of 10-11oC it survived a drop to 3 mg l-1 dissolved oxygen. During the incubation the fry tolerated a short-lived water temperature increase to 28oC.
Lenok is a predatory fish. During the first years it feeds mainly on benthic invertebrates and flying insects, giving preference to larger ones, such as gammarids, beetles, molluscs, larger dipteran larvae. Chironomid larvae and oligochaetes are eaten less frequently. When sexually mature, lenok feeds on small fish. It feeds all year around. Feeding cultured lenok commercial feeds has not been tested but it is believed that lenok would probably grow faster than under natural conditions. As lenok feeds at the bottom, one should apply sinking pellets.
In Lake Markakol males and females have a similar growth rate. The usual body weight reached is 2-3 kg, the maximum weight is 5-6 kg (Table 1). In aquaculture lenok reaches marketable size in the second or third year.
Table 1. Length and weight of lenok in lake Markakol
Lenok is a tasty fish which remains fresh for some time, allowing it to be transported chilled over long distances. It tastes good when cooked, fresh or salted. Local people preserve lenok by dry salting to obtain a high quality product which will last long. The eggs of lenok are almost as highly priced as those of the Far Eastern salmon from which a high quality red caviar is obtained. Lenok eggs, about 4 mm in diameter, can be salted, which makes them soft. They have a high nutrition value and delicate taste. In the 19th century and during the first half of the 20th century lenok was fished mainly for its eggs.
A special area on Lake Markakol has been designated as protected habitat for lenok and Arctic grayling. Here only angling is allowed, and this has led to the rehabilitation of lenok stocks.
2.3 Arctic grayling - Thymallus arcticus is a common fish of Siberian rivers, especially in the upper reaches, and in coldwater lakes where it has evolved into local races. It is present throughout the Altai mountains, in the drainage of the Irtysh, and in some other rivers. An isolated population exists in Lake Markakol. It inhabits both the large left-hand tributaries of the Irtysh and streams which are too small for taimen and lenok. It easily adapts itself to small streams, which would make it suitable for introduction in mountain rivers of Tien Shan and Pamir. At present Arctic grayling represents an insignificant part of commercial catches, but it is a good angling fish.
Arctic grayling spawns early in spring. Before the ice cover breaks the fish starts moving upstream to its spawning grounds, which are usually in the uppermost sections of rivers and streams. After spawning it migrates back but some fish stay permanently in the upper courses. In Lake Markakol females lay on the average 1500 eggs. In other streams their fecundity could be higher, but data are not available. The eggs are deposited on larger pebbles and water carries them downstream. The orange or grey-orange coloured eggs are 2.6 mm in diameter. The eggs need a temperature of 4-12oC and about 200 days to incubate. About a week after hatching the fry starts to actively seek food.
Adults feed on benthic invertebrates and flying insects. Some plant material is also eaten in autumn and fish are eaten in early summer. The fish is a facultative predator. In rivers the fish grows slower than in lakes. Some individuals reach sexual maturity when 2 years old, about 18 cm long and 90 g in weight. Some 2-year-old fish may reach 1 kg in weight. In both commercial catches and those of anglers fish of 150-300 g dominate. Arctic grayling is highly praised for its good tasting flesh. Perhaps it would be possible to raise it in fish ponds and feed it on trout feed.
Arctic grayling is highly valued by anglers and its introduction elsewhere has been considered. However, Arctic grayling might compete with trout. After rainbow trout was introduced in Lake Markakol it never appeared in fish catches and it is believed that this was due to competition from the trout.
2.4 Balkhash marinka - Schizothorax argentatus is present in all catchment rivers of Lake Balkhash and Lake Issyk-kul, and until recently it was also found in the lakes of both basins. More recently the stocks of this fish have drastically declined. Marinka appears in several forms as the species has adapted itself to a variety of habitats. A semi-migratory lake form differs from a typical riverine form in feeding habit and in growth rate, with the riverine forms being a slower growing fish. Both forms still require the same habitat for their spawning, i.e. a fast-flowing current over stony bottom.
Females mature when 4-11 years old, males at 3-8 years of age. Fecundity is a high 12,000 to 122,500, with the numbers of eggs usually ranging from 32,000 to 67,000, depending on the age structure of the spawning stock. An egg has a 2.3 mm diameter. Under controlled conditions at a water temperature ranging from 15 to 16oC the eggs hatch on the 5th day. The process of hatching takes 24-32 hours. At a temperature of 13oC the hatching lasts up to 45 hours. Six days after hatching the yolk sac is fully absorbed and the 9-10 mm long larvae start feeding on plankton. At the age of 25 days the fry already has a fish form. Trials to incubate marinka eggs obtained from natural spawning as well as by stripping have been unsuccessful. The survival of larvae is closely related to the egg quality. This can be determined from the diameter, weight and content of fat, carbohydrates and protein of eggs. During the first days of active feeding the larvae feed on phyto- and zooplankton. When their body length reaches 16 to 30 mm they start feeding on microzoobenthos and bottom algae.
In some carp pond farms the river form of marinka is considered undesirable. It would appear that in ponds marinka directly competes for food with carp. Marinka adapts well to artificial feeds, including those low in protein content. Under natural conditions, three feeding types of marinka can be distinguished. The mountain river form, which feeds mainly on benthos and neglects flying insects, is adapted to feeding on attached algae and higher plants. Its lower jaw is adapted to scraping. The lake form also feeds largely on plant material. In large rivers marinka is often a facultative predator if there are no other predators. It then feeds mainly on benthic organisms, flying insects, small vertebrates such as lizards that have fallen into water, and on small fish, particularly stone loach. The form which feeds on plants is the most suitable for growing under controlled conditions, including artificial reproduction, and it is also suitable for introduction into other water bodies. In such water bodies, if benthos-feeding fish are already present, it can exist almost entirely on algae and detritus, with only a small addition (about 6%) of food of animal origin. It feeds mostly on Characeae which are avoided by other fish with the exception of grass carp.
The growth rate depends on the type of nutrition and on the water body inhabited by marinka. In mountain streams the fish seldom reaches more than 1 kg. The weight of the sexually mature montane form usually ranges from 100 to 300 g. Individuals of the lake form are heavier, usually 1.5 kg, but some individuals may reach 5-6 kg. For the purpose of fisheries the lake form females should be 1 kg and the males 400 g. The facultatively predatory form may reach up to 12 kg, but usually is 2 to 5 kg.
The diversity of forms makes marinka a suitable fish for coldwater aquaculture. If fed suitable feed, probably of a higher protein content than that available under natural conditions, one would expect a faster growth rate and earlier maturing stocks. The adaptability of marinka is also shown from its presence in Lake Balkhash which is saline. It could therefore be introduced in other saline lakes with suitable temperatures and food supply. The major constraint in such water bodies could be lack of suitable spawning sites. This could be overcome by regular stocking of such water bodies with fingerlings produced under hatchery conditions.
2.5 Scaleless osman - Dyptichus dybowskii. Lake Balkhash drainage represents the northern limits for the distribution of osman. Individual fish have been found in mountain rivers of the southern slopes of Altai in northern Dzhungaria in China. These rivers run in the direction of the Black Irtysh, but do not reach it. In rivers in southern Dzhungaria (Kazakhstan), which belongs to the Balkhash zoogeographical Province, scaleless osman is a common fish. It also appears in several forms. It is confined to the mountain and foothill water bodies. In the Lake Balkhash drainage osman does not appear in rivers and small shallow water bodies located below the altitude of 600 m. It is common between 800 and 1500 m altitude, where it inhabits predominantly fast running mountain streams. There osman seeks quiet places under roots of overhanging trees and bushes, bigger stones and undercut banks. It readily migrates to lakes where it is a common fish. In lakes it grows faster than in rivers. It grows to the largest size in Lake Issyk-kul, in which, however, it is a rare fish. In the Altai region only the benthos-feeding scaleless osman is present. It feeds largely on gammarids, less on flying insects, occasionally on aquatic plants. The spawners are 15-25 cm long, but some sexually mature individuals may be only 7 cm and weigh 5 g. With such a small size and the relatively large eggs (2.3 mm in diameter), the fecundity is low, ranging between 1400 and 12,500 eggs. Females either lay all eggs at once or in batches on stony substrate at a temperature of 9-10o C. Scaleless osman breeds from May to September.
The eggs and peritoneal membrane of scaleless osman and marinka are toxic to humans. Cases of poisoning by salted or insufficiently baked eggs have been reported. Generally, however, proper cooking removes the toxicity and fishermen regularly eat boiled or baked fish eggs, especially those of marinka.
Owing to its slow growth and poor taste, scaleless osman in water bodies in the catchment of Lake Balkhash has no commercial value, nor is it captured by anglers, as it is a rare fish and more difficult to catch than Arctic grayling or trout. However, in the southern part of its distribution area, i.e. outside the regions covered in this paper, osman is also fished.
2.6 Scaled osman - Dyptichus maculatus . In the north its distribution is similar to that of the preceding species, i.e. it does not reach beyond the Balkhash catchment. The species inhabits the upper-most stretches of rivers and mountain lakes located above 1200 m. At the age of 7 years the fish reaches 15-20 cm, and the largest specimens found were 25 cm long and 11 years old. Females produce 1000-5000 eggs which have a mean diameter of 2.6 mm. The eggs are not poisonous. They are laid in batches. Scaled osman has no commercial importance, nor is it targeted by anglers.
Scaled and scaleless osman, stone loach (Noemacheilus) and minnow (Phoxinus) are preyed on by Arctic grayling, taimen and the introduced rainbow trout.
Fish introductions have had a profound impact on the fish fauna of the Balkhash basin. Where there were formerly only 14 indigenous species, there are now 40 species. Similar changes have taken place in other river/lake basins without outflow, such as in the drainage area of the River Talas (Kyrgyzstan/Kazakhstan). To improve the fish production in water bodies of Central Asia, such as Lake Balkhash, the Alakol lakes and Lake Zaysan, (the last now submersed by Bukhtarminsk reservoir on the River Irtysh), inter-basin transfers, and in some cases regular releases and stocking have been carried out. This has had a profound impact on the indigenous fish stocks in Lake Balkhash (Petr, 1992), Lake Issyk-kul (Savvaitova and Petr, 1992; and this volume), and in numerous reservoirs of Central Asia in which the original fish stocks were those of the dammed river (Petr, 1995). The indigenous fish species have usually decreased in number and their proportion in commercial catches have declined, while the proportion of the introduced fish in fish landings has increased. The overall result has seen little change in the total fish production, unless the new mix of fish stocks became overfished, and then crashed. The impact of planned and inadvertent introductions on native fish in mid Syr Darya basin has been reviewed by Salikhov and Kamilov (1995).
3.1 Alakol lakes
Three large water bodies in the region have became a unique experiment in testing the possibility of increasing fish production through the introduction of fish and invertebrates. These are the Alakol lakes, Lake Balkhash, and Lake Zaysan/Buktarminsk reservoir on the River Irtysh.
In 1932-1933 about 1000 broodstock wild carp were released in Alakol lakes. In 1930, while commercial fishery was just beginning on these lakes, the total catch was 385 t yr-1, of which 65% was marinka, 31% perch, and 4% common carp. By 1944 the total catch more than doubled and reached 750 t, of which common carp was 73%, perch 25% and marinka just 2%. It is estimated that in the 50 years since the start of the fishery about 100,000 t of carp were captured from the Alakol lakes. The introduction has yielded about 2 t per each brood fish stocked. However, marinka was totally displaced and has not appeared in catches since 1970. The highest yield of common carp was 13.2 kg ha-1 recorded in 1963-1964, and that of perch was 2.8 kg ha-1. During 1963-68 more than 7000 mature pikeperch were released in the Alakol lakes. This predator destroyed the remaining marinka stocks and began to feed on perch and stone loach, and later on common carp, because there was no other fish to feed on. This has resulted in the decline of the stocks of carp and perch. Over a 20-year period 13,300 t of pikeperch were captured, at an annual rate of about 700 t, which is poor compensation for the 3500 t of carp captured annually before the introduction of pikeperch. To remedy the situation, 20,800 bream of different age were released during 1987-88. Perhaps this may result in changing the Alakol lakes into a bream-pikeperch water body.
3.2 Lake Balkhash
The wild form of common carp (Cyprinus carpio) was the first fish species introduced in 1905 in Lake Balkhash (Table 2). This fish was transferred from the Chu River, an isolated drainage area, situated in the Aral Sea basin. Wild carp soon started displacing marinka. Immediately after the common carp introductions in the lake, dace began to appear in the lake. This could be the result either of its transfer in 1928-29 from the Irtysh basin, or possibly it was always present in the lake, but never identified. Then followed the introduction of spiny sturgeon and Turkestan barbel, which did not result in any greater changes in fish stocks. In 1948-49 appeared tench, bream and crucian carp. Bream soon appeared all over the lake. Within the next 10 years Lake Balkhash received a number of fish species from the Amur River basin, which entered the lake together with the planned releases of Chinese carps (grass carp and silver carp). Pikeperch from the Ural River was also introduced. This started an irreversible process of changes in fish stocks with the following sequence in the dominance of species in fish catches. In 1941 common carp represented 69%, marinka 8%, and perch 23% of the fish catch. In 1950 the commercial catch consisted of common carp (72%), marinka (16%) and perch (12%). In 1960 it was 76% of common carp, 11% marinka, 12% perch and 1% bream. Pikeperch first occurred in 1961 (1% of the catch). Major changes started in 1964 when common carp represented 58%, pikeperch 32%, marinka 6%, perch 2%, bream 2%. In the six following years pikeperch decimated perch stocks and heavily reduced those of marinka, but the total fish catch doubled. High catches persisted for the following 10 years. In 1969-70 wels, asp and roach appeared in catches, and by 1976 the proportion of pikeperch began to fall, with a parallel increase in bream. In 1980 the catches were as follows: bream - 73%, pikeperch - 14%, common carp - 4.5%, wels - 4%, asp and roach - 1% each, and other fish species - 2.5%. Roach was introduced in Lake Balkhash in 1965 as food for pikeperch when pikeperch started to decline. By 1984 bream fully dominated in catches (79%), followed by pikeperch (8.5%), wels (4.5%), roach (4.5%), common carp (2%) and asp (1.5%). The total annual catch equalled catches of the period 1941-61, i.e. the period before the "restoration" of Balkhash fish stocks was initiated. Thus, the introductions of new fish species and their invertebrate food organisms led to dramatic
changes in the fish species composition and in quantitative relationships among species, and to a temporary increase in fish catches due to the overexploitation of the indigenous species. The effort resulted in an extra catch of 65,000 t over the period 1961-1984.
The manipulation of fish stocks took place during a fluctuating lake level. The fishery management was based on a traditional approach of increasing fish stocks through introductions and on attempts to maintain the indigenous fish stocks, but the intrinsic processes within the ecosystem were more powerful than human interventions. Because of the lack of enforcement of the existing fishing regulations, stocks of pikeperch, roach, and to a lesser degree of bream and wels declined. The great expectations from the introduction of Chinese phytophagous fish have not materialised. However, their introduction into pond culture reoriented the cultured fish production from common carp to Chinese carps, which in turn resulted in a substantial increase in aquaculture production.
Due to the difficulty of separating specific seed material in the early live stage when such material is obtained from the wild or from non-monospecific aquaculture, other species were inadvertently introduced with the planned introductions. Some of the species introduced in this way, such as wels, Volga zander (Stizostedion volgensis) and crucian carp, became important for fishery. Two other species, i.e. dace and tench, are favoured by anglers. Only the intentionally introduced bream, pikeperch, roach and common carp brought the expected commercial effect. Expectations from the introduction of spiny sturgeon and trout have not been fully realised. Similarly, the Chinese carps have failed to result in a significant increase in fish production in open waters. Introductions of coregonids have failed, both biologically and commercially. According to Tereshchenko and Strelnikov (1995) the major impact had the introduction of pikeperch, and later of catfish and asp. This led to the breakdown of the established relationships among fish species and to redistribution of ecological niches in the ecosystem.
3.3 Lake Zaysan/Bukhtarminsk Reservoir (Irtysh basin)
In the Irtysh basin (Table 3) only one of the unintentionally introduced species - Pseudorasbora parva - has survived. While the majority of introduced species failed to adapt to Bukhtarminsk reservoir conditions, three species were beneficial for the fisheries: bream, common carp and pikeperch. Results of the introduction of lenok from Lake Markakol are difficult to evaluate as lenok was always present in the rivers entering the reservoir, but never occurred in the River Irtysh and in Lake Zaysan which is now part of the reservoir. This flatland reservoir does not seem to meet the requirements of the mountain river lenok. On the other hand the reservoir might be suitable for the lake-type lenok from Lake Markakol. Rheophilic fish of mountain streams may establish healthy stocks in reservoirs and lakes only if a vacant niche exists. The absence of this could be the reason why both lenok and the Balkhash marinka (Schizothorax argentatus) failed to establish themselves in the reservoir.
3.4 Mountain rivers of Tien Shan
In mountain rivers of Tien Shan fish stocks are mostly underexploited. The indigenous fish stocks are poor in species and no exotic species have been introduced there. Some of the rivers could perhaps be used for coldwater fish culture, as they have high quality water. Marinka, and to a lesser degree the scaleless osman, are two fish species interesting from the fishery point of view. Other species are not commercially valuable, apart from their value as forage fish for the piscivorous species, either indigenous or introduced.
The current poverty of fish species in these rivers and the purity of indigenous fish stocks contrast sharply with the situation in rivers and lakes of the adjacent plains. Introductions of fish there have resulted in the presence of new fish communities, with the exotic fish species often displacing the indigenous fish. In Lake Balkhash the only commercially valuable indigenous species is Balkhash marinka, whereas other indigenous species, such as stone loach and minnow, now serve as food fish for introduced fish such as trout and Arctic grayling.
3.5 Criteria for introductions
The success and failure of fish introductions in coldwaters and lowland lakes of Kazakhstan and Central Asia have a number of different causes and each water body has to be dealt with separately to understand what has happened. Nevertheless, some factors are common to several water bodies and their identification may assist with the formulation of future fishery management strategies.
An important finding is that when older fish are introduced and later regularly stocked, the results are better as the mortality of older stages is lower than that of eggs and fry or small fingerlings. If adult fish are introduced, some species of fish are capable of producing the first local generation already one or two years after their introduction. When adult fish are introduced, the success may be detected in fish catches earlier than when there are repeated introductions/stocking of young stages. Furthermore, if the wrong species is introduced as adults and proves unable to adapt to the new water body, this would show itself within a short time as the species would not appear in the fish catch. This would result in considerable savings of money and time spent on producing more (young) material for carrying out stocking with hope that eventually such a species would become established. Where such unsuccessful stockings are made, they are usually combined with fishery restrictions, and under some circumstances the fishery may become uneconomic.
A good knowledge of ecosystem interrelationships is another important factor which may decide on the success of an introduction. The purpose of introductions is usually one or more of the following:
The last two points may not have direct economic importance.
After each introduction the manager needs to make a thorough analysis of the impact of the introduction on the existing fish stocks and aquatic environment, including the fish food availability. Mostly, there is little monitoring after introductions are made. Research may also assist in clarifying some unsuccessful introductions. An example is Lake Zaysan, now part of Bukhtarminsk Reservoir on the Irtysh. Studies of sediments have shown that not so long ago common carp, bream, pikeperch and several other fish species of the Ponto-Caspian fish fauna inhabited the lake. Their disappearance was the result of a change in climate. An attempt to re-establish these species in the lake failed due to pressure from fish species now present in this lake/reservoir system.
Transfers of fish from one water body to another with similar fish faunas gives better results because such introductions do not lead to severe competition among species. The more distant geographically and faunistically the species, the more difficult it may be for it to settle into the new environment. Where the introduced species competes with other fish for the same ecological niche, the potential for its successful establishment is poor.
Most successful introductions are those into isolated lakes, such as Lake Balkhash. Their fish species communities are limited in number of species and have been isolated for a long time, not having any contact with widely distributed fish species. This has resulted in poor resistance to competitors which are highly adaptable in terms of food, spawning areas and changing environment, such as that occurring under the impact of human activities influencing water quantity and quality. In Lake Balkhash the ichthyofauna had no contact with the neighbouring faunas of the River Ob basin in the north and with the Ponto-Caspian basin in the west and south. Lake Balkhash was colonised by marinka, osman and stone loach from the river systems of Tien Shan. Later on minnow and Balkhash perch arrived from the north. The vacant lake niches were thus occupied by riverine fish which had no need for a narrow niche. When fish were introduced from catchments of the Caspian, Aral, Ob and Amur, the newcomers dealt with the indigenous species very rapidly. The formerly riverine montane fish fauna was especially vulnerable to the impact of the introduced piscivores. It showed that a fish species community which existed for a long time without the presence of predatory fish species, has weak protective mechanisms against such enemies. To develop such mechanisms requires some time, which was not available. This presumption is confirmed also by the situation in mountain rivers and streams in which rainbow trout was introduced: the northern Tien Shan fish are threatened by this species in the same way that the indigenous species of Lake Balkhash are threatened by pikeperch and wels.
3.6 Rainbow trout introductions
Lake Nizhniy Kulsai in Tien Shan has become a reservoir dominated by rainbow trout. The establishment of rainbow trout in this lake has been followed for over 20 years. The introductions into Lake Kulsai started during 1964-66, when 220,000 rainbow trout eggs were imported from Czechoslovakia, and after their incubation 3000 fry were released in 1965 in Nizhniy Kulsai and 2000 in the River Kulsai. In 1969 5000 fry were also released in Lake Sredniy Kulsai, and in 1970 5000 were transferred from the new Turgen trout hatchery on Lake Kaindy. Floods in 1966 washed out the complete stock of rainbow trout from the hatchery into the Chilik River. Part of the stock was returned to the hatchery where it formed broodstock for further propagation.
Rainbow trout, introduced in Lake Nizhniy Kulsai, Lake Kaindy and into some rivers, joined the existing local fish fauna of scaleless osman and Tibetan stone loach. Everywhere it adapted extremely well to the local conditions, started feeding on the available food and achieved reasonably good growth rates. In Lake Kaindy, which had no fish, it fed on benthic organisms and flying insects, but in Nizhniy Kulsai it quickly decimated the local fish fauna. In water bodies of Tien Shan rainbow trout matures when three years old. No fish older than 6 years has been captured. This is explained by the shortage of food. Cannibalism was observed in the eighth generation, and some trout were found with plant material in their stomachs, both being indicators that the trout stocks were exceeding the carrying capacity of the water bodies in which they were introduced. The fecundity of females also declined. While the first females in Lake Nizhniy Kulsai at a body weight 1900-6100 g produced 3000-11,000 eggs, and those in the River Kulsai 1500-2000 eggs (body weight 500-600 g), females of 7-9 generations had only 1000-1400 eggs (body weight 200-510 g, age 3-4 years). During the spawning season the lake and river trout populations meet on spawning grounds in rivers..
The process of formation of trout stocks in water bodies of Tien Shan usually shows the following pattern, with some differences in the individual stages.
Stage 1: survival of the introduced fish and their reproduction in the new environment. This stage continues until the onset of spawning and production of the first local generation. It is characterised by rapid growth and development of gonads. The rate of maturation depends on the water temperature. Eggs are released over a long period. Trout is targeting food organisms which have high calorific values and are easily accessible. This stage lasts for about 5 years.
Stage 2: reproduction of the introduced fish and increase in numbers due to the abundant progeny. The fish starts consuming a wider range of food, but the growth rate is slowing down. The onset of sexual maturity and the time of reproduction stabilise. This stage lasts for 3 to 5 years.
Stage 3: fish stocks at their maximum numbers. Some typical food organisms almost disappear, and trout compensates for their loss by using other food sources, which, however, are of low quality. This results in a slower growth rate and reduced fecundity.
Stage 4: decline in fish stocks, increase in competition within the trout fish stock. Food intake is low, start of cannibalism. Appearance of dwarf males.
Stage 5: in Tien Shan water bodies trout stocks become stabilised 12 to 15 years after their introduction. Intake of food increases, growth rate is better than in stage 4. Cannibalism almost disappears, and dwarf males are absent. The stock density is close to optimum.
The experience from the introduction of trout in Tien Shan water bodies shows the need for close management of the introduced stocks from the beginning. To make use of the high production during the first two stages, the excess production should be fished out, to avoid the problems of the fourth stage.
There was no success with the introduction of rainbow trout in Dzhungaria. Introductions of fish such as Arctic grayling or lenok into the local rivers would be more successful than introducing rainbow trout.
3.7 Coregonid introductions
The following experience has been obtained from the introduction of coregonids in lakes of northern Kazakhstan. Six species have been introduced: European cisco (Coregonus albula), Arctic cisco (Coregonus autumnalis), Lake Chud whitefish (Coregonus lavaretus maraenoides), muksun (Coregonus muksun), Sevan whitefish (Coregonus lavaretus sevanicus) and northern whitefish (Coregonus peled). Usually, two to three species were introduced simultaneously. Muksun and Arctic cisco were introduced only once and resulted in a failure. Northern whitefish and other coregonids were released at the same time into over 30 lakes and reservoirs. In a number of lakes coregonids started reproducing, mostly producing hybrids. Coregonid stocks are regularly enhanced by releases of hatchery produced fry. The purpose of introducing coregonids, especially the northern whitefish, was to increase commercial fish catches. Coregonids reached the size of table fish in 2-3 years, but their quality differed, depending on their type of food. The best species proved to be the northern whitefish, which showed the fastest growth rate and produced the best flesh (Table 4).
During the first years after introduction the growth rate was the highest, later on slowing down as food supplies became less available. In Lake Malyi Tarangul the two-year-old fish had the following average weight: in 1981 - 484 g, 1982 - 365 g, 1984 - 238 g, 1985 - 120 g. Within five years the species lost much of its commercial value.
Today, in northern Kazakhstan fry of the northern whitefish is produced in hatcheries and regularly stocked. Fecundity of the northern whitefish ranges from 14,000 to 86,000. The fish spawns from the end of autumn to the beginning of winter, sometimes already underneath ice cover.
Mountain water bodies of Altai, Kazakhstan Dzhungaria and northern Tien Shan represent a good potential for various forms of coldwater fisheries including recreational fisheries. Fish species highly prized by anglers can be introduced in some mountain streams, while stocks of species of commercial importance can be either enhanced, or new species introduced into lakes and reservoirs. Large lakes of the submontane semi-arid zone offer a challenge of developing ecosystem-based fishery management instead of the prevailing extensive fishery. Selective fishing for introduced fish should go hand in hand with the protection of the depleted indigenous fish stocks. A good way of safeguarding the protection of indigenous fish species is their inclusion in pond fish culture. Development of artificial breeding methods for native fish should also assist in saving such species from extinction and stocking them would help in water bodies in which they are threatened either by overfishing or by competition from introduced species. Culture of rainbow trout should be given preference over the introduction of this very competitive fish species in waters with native coldwater fish species. Minimising human impacts resulting from the regulation of rivers and streams, and impacts of pollution, are important conditions for retaining healthy fish stocks and developing their potential for commercial and sport fisheries.
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1 Geographical names in tables may have slightly diferent spellings than those in the text. This is because the tables were typed before the text terminology was standardized.