Boundaries

The ecoregion encompasses the Upper Syr Darya [Sirdaryo] and Talas River basins within the Northern Central Asian Highlands. The Turkestanskiy and Alayskiy ranges form the southern border of the ecoregion, dividing the Zeravshan and Kyzylsu [Qizilsu] (Vakhsh) headwaters [631] from the Syr Darya [Sirdario] tributaries flowing to the Ferghana Valley. The Terskey Ala-Tau Range [Teskey Ala-Too = Teriskey Alatau Zhotasy] and the Dzhumgoltau [Dzhumgal-Tau] Range divide the ecoregion from Lake Issyk Kul - Chu [627]. Within the ecoregion, the Talasskiy Alatau Range [Talas Alatau Zhotasy = Talas Ala Toosu ] divides the Talas River drainage with the Naryn, Chirchik [Chirchiq] tributaries (Pskem and Chatkal), and Arys’ headwaters. The Karzhantau Range, and northwestern spurs of the Pskemskiy, Chatkal’skiy [Chotqol], and Kuraminskiy ranges form the western border of the ecoregion. The northern part of the ecoregion includes the drainage area of the Talas River, and the rivers flowing from the southern and eastern slopes of the Karatau Range [Qaratau Zhotasy].

Topography

This is a mountainous ecoregion, with elevations ranging from 215 m to over 5500 m above sea level. The Syr Darya River drainage is 462,000 km² in area, of which about 220,000 km² is mountainous. The average altitude of the Syr Darya drainage is much lower than that of the Amu Dar’ya drainage; therefore, perennial snow and glaciation are less notable here.

Freshwater habitats

The Naryn River begins at the confluence of the Bolshoi Naryn and Malyi Naryn rivers. The main tributary of the Naryn is the Kum-Tor River that flows out of the Petrov Glacier (16.8 km long). The length of the Naryn (from the source of the Bolshoi Naryn) is 722 km, and its drainage area is 59,110 km². The Burkhan River is the main tributary of the Malyi Naryn. It is formed by numerous streams flowing out of glaciers on the northern slopes of the Dzhetymbel Ridge. After the confluence of the Bolshoi Naryn and the Malyi Naryn, the Naryn River valley narrows into a ravine, where rifts abound and the river flow is turbulent. The Naryn joins the Kara Darya and loses its mountain character in the Ferghana Valley.

The Kara Darya River (length 177 km, area 28,630 km²) forms from the confluence of the Tar and Kara-Kuldzha rivers, which originate on the slopes of the Ferghana and Alai ridges. The Kara Darya begins in a wide valley in a strongly branching channel, bursts through the Kampyrrvatskoye Ravine, and then flows over a swampy floodplain, splitting into several branches in the Ferghana Valley.

From the area of the confluence of the Naryn and Kara Darya, the Syr Darya flows over the Ferghana Hollow, where it receives a large number of tributaries on the right flowing down from the Kuramin and Chatkal ridges. The larger left tributaries (Isfairam, Sokh, Isfara, etc.), flowing down the northern slopes of the Turkestan and Alai ridges, do not reach the Syr Darya because their waters are diverted for irrigation

Reservoirs such as Farkhad, Kayrakkum, Toktogul’, Charvak, and Bol’shoy Ferganskiy Canal have changed the general topographic pattern of the drainages.

The Talas River drainage covers an area of approximately 16,200 km², of which 10,800 km² belongs to Kyrgyzstan, and the remaining 5400 km² belongs to Kazakhstan. The Talas River rises from the confluence of two large rivers: Karakol (Aral-Talas) and Uch-Koshoy (Chichkan-Talas). The Karakol River begins 100 km from the village Chat-Bazar, at an altitude of 3300 – 3500 m above sea level in glaciers along the southern slopes of the Alexandrovskiy Ridge. The Uch-Koshoy River is fed by glaciers and some springs on the northern slopes of the Talas Ala Tau Mountains.

The Talas River flows westward for 90 km down to the Ulkun Ravine. After the village Alexandrovka the Talas passes between the Ichkele Tau and Ak Tash mountains, forming the Ulkun Ravine (Aleksandrovskoye Ravine). The river emerges from the ravine into the Aulieatin Plain, from which it flows northwest 200 km. Around 100-150 km from the left bank of the Chu River, the Talas River dissipates into separate branches and lagoons in the sands of the Muyun Kum Desert.

The Ters River rises on the southern slopes of the Karatau Ridge (Zhambyl Region). The Ters-Ashchibulak Reservoir was built at the outlet of the river from the mountains. In some years the Ters-Ashchibulak Reservoir stops the flow of the Ters River. After the reservoir the river receives a number of small tributaries. It is called the Assa River on the plain. 

Lake Bilikol’ lies at the eastern foot of the Karatau Ridge and is the first and largest lake on the Assa River. Other lakes downstream include lakes Bugul’kol’, Akkol’, and Ashchikol’. The last lake of the system, Ashchikol’, is saline, whereas the others are freshwater lakes. Because the connection between the lakes is not constant, water does not reach Lake Ashchikol’ every year, resulting in its desiccation. Lake Akkol’ is an artificial lake. At present it is divided by dykes into separate water bodies.

The hydrological regime of the Syr Darya is affected by glaciation and perennial snow. The rivers fed by glaciers and snow include the Bolshoi Naryn and Malyi Naryn, as well as left tributaries of the Syr Darya (Aksu, Isfara, Sokh, Shakhimardan, Isfairam and others). These rivers flow down the Turkestan[skiy] and Alai[skiy] ridges, which are the tallest ridges of the drainage. The largest tributaries of the Syr Darya (Naryn, Kara Darya, Chirchik) are also fed by snow and glaciers. Spring tide caused by snowmelt occurs in March and April. In May a second major flood begins, reaching its maximum in July. The minimum discharge is observed from December through January.

The Syr Darya is characterized by a notable solid discharge that averages 540 m³ s^-1. Under the natural hydrological regime mean annual turbidity equals 1550 g m^-3, and the maximum turbidity of the river reaches 3140 g m^-3in May within the Ferghana Valley. Water turbidity has declined considerably with the construction of reservoirs.

Terrestrial habitats

Vertical zoning is highly pronounced, from montane glaciers down to lowland deserts. Terrestrial ecoregions include Central Asian northern desert, Gissaro-Alai open woodlands, Tian Shan foothill arid steppe, Tian Shan montane steppe and meadows, Tian Shan montane conifer forests, Alai-Western Tian Shan steppe, and Pamir alpine desert and tundra.

Description of endemic fishes

The ecoregion contains a handful of strict endemics, including Cottus jaxartensis, tubenose sculpin (C. nasalis), and Turkestan sculpin (C. spinulosus) from the Upper Syr Darya drainage. There are varying opinions in the literature on their status and relationships. Further taxonomic revisions are needed.

Schizothorax saltans (Turdakov 1955) is another strict endemic only known from its original description. No specimens have been collected since that time. Lake Ashche-Kul [Ashchikol], from where it was discovered, has been transformed for irrigation, and its tributaries have been regulated and converted to canals.

Syr Darya sturgeon (Pseudoscaphirhynchus fedtschenkoi) is the only species of Pseudoscaphirhynchus endemic to the Syr Darya basin (near-endemic to ecoregions 626, 628). It is well-adapted to life in turbid flows. After the construction of river channel reservoirs where suspended particles are sedimented, water in the Syr Darya became much more transparent, which negatively affected the Syr Darya sturgeon. It has now probably disappeared in the middle reaches of the Syr Darya; the most recent records of catches are dated 1972.

Tashkent riffle bleak (Alburnoides oblongus), Syr-Darya dace (Petroleuciscus squaliusculus), and Kuschakewitsch loach ("Nemacheilus" kuschakewitschi) are also near-endemic, and are mostly distributed in the middle reaches of the Syr Darya River up to the Ferghana Valley. These small fishes occur sporadically, but are numerous in areas where their habitat occurs. However, there are no reliable data in collections.

Other noteworthy fishes

Dzihunia turdakovi (Prokofiev 2003) is a newly described species only known from one specimen from the upper Talas River in Kyrgyzstan.

Gymnodiptychus dybowskii kessleri belongs to the complex Gymnodiptychus dybowskii s.l., naked osman, which includes at least five different subspecies or distinct species. The complex has not been revised, so we distinguish subspecies following Turdakov (1963).

Sary-chilek marinka (Schizothorax intermedius eurycephalus) is part of a widespread species complex that needs revision. We follow Turdakov’s (1963) taxonomy of the complex. Schizothorax intermedius talassi is another endemic subspecies that is poorly known with no reliable data on its biology and abundance.

"Nemacheilus" kuschakewitschi badamensis and Triplophysa coniptera salari are stone loaches known only from their original descriptions.

Talas dace (Leuciscus lindbergi) and Talas loaches, Triplophysa coniptera and T. paradoxa, have been drastically reduced, and are now only recorded from the mountainous part of the basin. There is no reliable data on their biology and abundance.

Triplophysa stoliczkai elegans and Diptychus gymnogaster oschanini have a doubtful taxonomic status. Morphlogical differences described in their original descriptions provide a good reason to re-evaluate their status as species. Revisions of Triplophysa and Diptychus are strongly needed.

Ecological phenomena

Similar to other highland ecoregions, the Upper Syr Dyra system is characterized by clearly pronounced zoning and diversity according to the type of water body. Most upland plains ("syrts") have a very limited set of species. The most common are Diptychus sewerzowi and Triplophysa stoliczkai elegans, which are highly abundant in shallow, warm, and slow-running waters of branches and oxbows. At the same altitudes, larger fast-running rivers are almost fishless, whereas their smaller tributaries are rich with T. stoliczkai elegans and naked osman (Gymnodiptychus dybowskii kessleri). Further downstream the fish assemblages are poor, with T. stoliczkai elegans dominating over scaly osman (D. maculatus) and Turkestan catfish (Glyptosternon reticulatum). Gray loach (T. dorsalis) occurs in oxbow lakes. Kuschakewitsch loach ("Nemacheilus" kuschakewitschi) is dominant in rivers just upstream from lowlands. Turkestan catfish, gudgeon (Gobio lepidolaemus), striped bystranka (Alburnoides taeniatus), and Bukhara stone loach (Dzihunia amudarjensis) are also abundant.

Justification for delineation

The ecoregion is the high-altitude section of the Syr Darya drainage. Besides inhabitants of mostly lowland sections of the Syr Darya basin, the fauna includes typical representatives of the Central Asian Mountainous fauna. It also includes the river and lake systems of the former Talas River drainage that occupies the Talas depression. The Northern Central Asian Highlands ecoregion displays clear affinities with the Lower and Middle Syr Darya ecoregion [626], but at least a third of the species and subspecies do not extend to the latter. On the generic level, the fauna of the Northern Central Asian Highlands ecoregion is closely related to the Upper Amu Darya [631] fauna, but somewhat different on the species level. This ecoregion also has Petroleuciscus and Cottus, which are absent from the Upper Amu Darya [631].

Level of taxonomic exploration

Fair to good in the lowland part; poor in some remote mountainous areas as well as the Talas River drainage. Balitoridae and Schizothoracinae need thorough revisions.