Large river mayfl ies (Insecta: Ephemeroptera) and their distribution in the Upper Volga River: current knowledge and conservation issues

Abstract

This article provides an overview on the mayfly species of the headwaters of the Volga River, and gives an indication on the general species composition in East European lowland rivers. Although research on mayflies has tradition in Russia, including some well known scientists, up to now no detailed distribution data on mayflies was available for the headwaters of the Volga Basin. During the research expedition Volga 2005 bottom samples were taken with a grab during the low-flow period. A preliminary checklist already revealed that the mayflies form a taxa-rich part of the benthic invertebrates. After identification it turned out that several typical large river mayflies occurred, which are nowadays rare in Europe. Along the 450 km sampling-stretch from the source to Tver, Ephemeroptera were present in all three geomorphological reaches and their abundance was found to increase downstream. From the material taken during the expedition in 2005, ten families and fourteen genera were identified. At locations where Ephemeroptera were present their total densities varied between 13 and 798 ind. m -2 . Frequent species were Pothamantus luteus, Ephoron virgo, Heptagenia sulphurea and Ephemera danica. The most remarkable species from the faunistical point of view was Prosopistoma pennigerum, which was recorded for the first time from Russia. In total 29 mayfly species were recorded in the headwater of Volga River up to now. The intact hydromorphology in the research area, which is reflected in a high amount of different mesohabitats, definitely supports an individual and species rich mayfly fauna, including several rare and threatened species. As some of these are considered being typical for large rivers at a European perspective, a major emphasis shall be put on the conservation of the intact riverine habitats in the Upper Volga River, supporting this typical and pristine mayfly fauna.