Surveys and field measures for nature conservation

Saving bivalves by their translocation on the Orlice River in Hradec Králové (eastern Bohemia)

Tuesday, August 20, 2013

A part of the bank wall close to the Morava/Moravia Weir, located on the Orlice River in Hradec Králové was restored in 2013. Planned building activities affected habitats inhabited by Specially Protected wild species occurring at the Orlice and Labe/Elbe Rivers Site of European Importance No. CZ 0524049 (SEI, pursuant to Act No. 114/1992 Gazette on Nature Conservation and Landscape Protection, as amended later, the term for the Site of Community Importance, SCI under the European Union’s Habitats Directive). The Natura 2000 site boundaries pass the Orlice river banks including the construction site. 


Before the restoration, the Orlice River water level had been decreased by approx. 0.5 meter. Thus, a river bottom became partially bare. Close to the river bank, bivalves were able to move to follow retreating water level, particularly because of diversified river bottom, presence of stones and other anthropogenic barriers. As required by a client, bivalves were translocated from the above construction site as well as from the respective part of the water stream reaching the next downstream Orlice River swelling.

In the course of the above activities, 19 bivalves belonging to four species were found at the construction site, namely: the Painter´s mussels (Unio pictorum), specially protected under Act No. 114/1992 Gazette on nature conservation and landscape protection as amended later, and Ministry of the Environment of the Czech Republic Decree No. 395/Gazette, as amended later, as Critically Endangered, the Swollen river mussel (Unio tumidus), classified as Vulnerable within the Red List of Threatened Invertebrates of the Czech Republic, the Depressed river mussel (Pseudanodonta complanata) and the duck mussel (Anodonta anatina). In addition, in total 132 other mussels were translocated from the Orlice River stretch from the Morava/Moravia Bridge up to the river swelling in Slezké Předměstí/Silesian Suburbs in Hradec Králové.