Freshwater molluscs of the Dyje (Thaya) River and its tributaries - the role of these water bodies in expansion of alien species and as a refuge for endangered gastropods and bivalves

Luboš Beran

doi:10.12657/folmal.021.018

Abstract

The malacofauna of the Dyje River, including the lower sections of its five tributaries, is still rich and diversified despite the pollution, regulation and building of several dam reservoirs. In total, 42 freshwater mollusc species (24 gastropods, 18 bivalves) were found at 75 sites. The richest malacofauna (30 species) was recorded in the lower section of the Dyje. Populations of endangered or rare molluscs Theodoxus danubialis, Viviparus acerosus, Lithoglyphus naticoides, Unio crassus, Pseudanodonta complanata, Pisidium amnicum and P. moitessierianum were found. The first three species inhabit only the area under study in the Czech Republic. Especially the occurrence of Unio crassus corresponds with river sections that were only partly affected by human activities (long distance below dam reservoirs, less polluted sections, unregulated watercourses). The occurrence of five invasive species, four originating from other continents (Potamopyrgus antipodarum, Physella acuta, Ferrissia fragilis, Sinanodonta woodiana) and one (Dreissena polymorpha) originally Ponto-Caspian, was confirmed for the Dyje River and its tributaries. The Dyje River formed the main invasion route from the Danube River into Moravia (eastern part of the Czech Republic).

Highlights

The Dyje (Thaya) River is one of the largest rivers in the Czech Republic and belongs to the Black Sea drainage area
42 freshwater mollusc species were found in the Dyje River and the lower sections of its five tributaries: 24 gastropods and 18 bivalves
Fourteen species were recorded in the upper section of the Dyje River (Dyje I, upstream of the Vranov dam reservoir), while in the lower section the molluscan assemblages included from 24–27 (27 in Dyje II; 24 in Dyje III – Vìstonice dam reservoir) to 30 (Dyje IV) species (Fig. 4)

Summary

Introduction

The Dyje (Thaya) River is one of the largest rivers in the Czech Republic and belongs to the Black Sea drainage area. The lower section of the Dyje River has been of interest to malacologists for more than 100 years. G. material deposited in the National Museum in Prague) till 1998 have been summarised in BERAN & HORSÁK (1998, 1999) who studied aquatic molluscs of the Dolnomoravský úval lowland, including the lower stretch of the Dyje. The macroinvertebrate fauna of the Dyje River downstream of the Nové Mlýny reservoir was studied by HORSÁK (2001). Aquatic molluscan fauna of the upper part of the Dyje was poorly known and no published data were available. Little attention was paid to the aquatic molluscs of the lower sections of its tributaries except for the Kyjovka River which was studied by BERAN & HORSÁK (1998)

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Discussion

Conclusion