CHIRONOMID FAUNA OF THE RIVER ANGARA

The Angara is the main river of Eastern Siberia. It flows out of the oligotrophic Lake Baikal and after 1779 km joins the river Yenissey. The water of the Angara remains baikalian for a significant distance. Even at the mouth of the river 45% of the total water is baikalian. According to R. A. GOLYSHKINA (1970) the substratum is composed mainly of stones, due to relief and geological structure. The Angara previously was a mountain river with a high current velocity of 7 km h-1 in depositing areas and 12 15 km h-1 in eroding areas.


Introduction
The Angara is the main river of Eastern Siberia.It flows out of the oligotrophic Lake Baikal and after 1779 km joins the river Yenissey.The water of the Angara remains baikalian for a significant distance.Even at the mouth of the river 45% of the total water is baikalian.According to R. A. GOLYSHKINA (1970) the substratum is composed mainly of stones, due to relief and geological structure.The Angara previously was a mountain river with a high current velocity of 7 km h-1 in depositing areas and 12 -15 km h-1 in eroding areas.

A
The Angara from the Lake Baikal outflow to Bratsk is divisible into three parts: 1) from outflow to Irkutsk, 2) from Irkutsk to the inflow of the river Kitoy, 3) from the mouth of Kitoy to Bratsk.
According to A. A. LINEVICH (1953A. A. LINEVICH ( , 1957A. A. LINEVICH ( , 1981) )  Robackia demeijerei (KRUS.)and Beckidia zabolotzkyi (G OETGH.), species not found in the upper parts of the river.There are pelorheophilic and psammorheophilic forms dwelling in silted sand: the most common among them are Polypedilum bicrenatum KIEFF., P. scalaenum (SCHRANK), Cladotanytarsus gr.m a n c u s (W ALK.), Chironomus gr.thummi (KIEFF.),and Ch.pr.plumosus-reductus LIPINA.Silt is inhabited by Chironomus gr.thummi.General features of the chironomid fauna of the lower part seem to be quite different from those of the upper parts.A rheophilic complex, including baikalian species and mainly composed of species belonging to the Diamesinae and Orthocladiinae, inhabits the typical stony biotopes of the upper parts of the river; this is replaced in the lower parts by a common complex of river forms belonging mainly to the Chironominae.In sandy biotopes the psammorheophils C. ra, R. demeijerei, and Bekidia zabolotzkyi are found.

Present state of the chironomid fauna after erecting the complex of dams
The river Angara is unaffected initially (about 7 km), from Irkutsk to settlement Telma (about 80 km) and below the dam of the Ust-Ilim hydropower station to its mouth (962 km).Close to its outflow from Lake Baikal the same species that dwelled here before the regulation remain; the 5 baikalian endemic species mentioned above are still to be found.Lithorheophilic forms found in the 40-s dominate.After the regulation in the middle 70-s we have investigated the river near Angarsk (at 10 km).Comparison of the chironomids before and after the regulation has shown some changes in composition (TOMILOV & al. 1977) At the end of the 80-s to the beginning of the 90-s we studied the chironomids of the Angara below the dam of the Ust-Ilim power station (KOZHOVA & al. 1993)

Conclusion
In the river Angara from its outflow from Lake Baikal to its junction with the River Yenissey hydrologic conditions change: decrease of current velocity, increase of water temperature, decrease of transparency, and increase in deposition of sand and silt, i.e. the transformation of a mountain river into the usual Siberian river, and consequent changes in the chironomid fauna take place.In the upper parts of the river lithorheophils of the subfamilies Diamesinae and Orthocladiinae prevail, whereas in the lower part, pelorheophils of the subfamily Chironominae dominate.The main characteristic feature of the river Angara -the influence of Lake Baikal on the fauna (the presence of baikalian endemics) -occurs mainly in the upper part of the river.
(In Russian)