Reconfiguration of the sluice on the Rehberggraben and improvements for the hard shelled river mussel population


Hard shelled river mussels are known to inhabit the Rehberggraben. This species is listed in Annex II of the FFR Directive and is the subject of special protection. Until now it has not been possible to halt the decline in the population of these mussels in spite of many measures taken in the areas in Bavaria and across the whole of Germany where they are known to exist. River development, predation by musk rats, intensive cultivation of adjacent fields right up to the water's edge and the introduction of sewage are amongst the most important causes for this decline. Measures to increase the hard shelled river mussel population therefore play an important part in the in the LIFE+ project.

Thus the pipe culvert in the Rehberggraben which was impassable to the mussels and their host fish was replaced in September 2012. A box culvert with a natural stream bed was constructed at this location; this culvert will in future no longer prevent the dispersal of this species.
Old pipe culvert on the Rehberggraben

New box culvert through which the mussels can now pass without restriction

In addition, the use of land adjacent to the FFH area changed to a less intensive form in order to create a buffer strip next to the water. As well as protecting the mussels, this margin is also a valuable habitat for many plant and animal species.

Photo: Turkish damselfly (Coenagrion spec.)