Level of study of aquatic invertebrates of the Komi Republic large rivers (Pechora and Vychegda)

Results of the study of the Pechora and Vychegda rivers aquatic invertebrates are described. It was found out that data on their quantitative development and distribution across longitudinal profile of the rivers is insufficient, though there were long stories of hydrobiological researches. 109 zooplankton species and forms in the Vychegda river, 73 - in the Pechora river, and 20 and 24 zoobenthos groups are known. These groups are more fully studied by the staff of the Institute of Biology - Mollusca, Oligochaeta, Hemiptera, Chironomidae, Ephemeroptera, Plecoptera, Trichoptera, Crustacea and Rotifera. The maximums of aquatic invertebrates diversity are noted in middle parts of the rivers. Rotifers dominate in zooplankton of the studied rivers, they are the most diversified and abundant. Zooplankton biomass is formed by Crustaceans. Zoobenthos distribution in the rivers depends on flow velocity and bottom substratum type. In the upper reaches of the rivers in mountain parts plankton is poor, and in benthos larvae of amfibiot insects it prevails. The middle course of rivers is rich in zoobenthos. Due to geomorphological conditions the invertebrate fauna in the rivers' middle course is studied better. In the Lower Pechora 40 zooplankton species and 15 zoobenthos groups, in the Lower Vychegda 53 zooplankton species and 4 zoobenthos groups are known. In the lower reaches of the rivers rather large abundance and biomass of aquatic invertebrates was registered.