Rapport sur les espèces macro-indicatrices de la qualité des cours d’eau. Répartition, Habitat, Mesures de protection et de restauration des populations

The Direction of the non-navigable watercourses of the Ministry of the Walloon Region
commited the realisation of a study on some flagship riverine or aquatic animal species to the
zoogeographical research unit’s care. The species were selected owing to their aquatic or
semi-aquatic life history traits and to their interest as bio-indicators of the quality of the
riverine habitats. Their patrimonial interest was also taken into account, some of them are
indeed concerned either by the Bird or by the Habitat directives (CE 79/409 and CE 92/43).
The next species were considered in this report: European otter (Lutra lutra), Dipper (Cinclus
cinclus), Kingfisher (Alcedo atthis) unionid mussels (Unio crassus and Margararitifera
margaritifera), water shrews (Neomys anomalus and Neomys fodiens), Sand martin (Riparia
riparia), bats (Chiroptera) and four species of damselflies :Onychogomphus forcipatus,
Oxygastra curtisi, Gomphus vulgatissimus, Cordulegaster boltonii.
The main life history traits of every species was reminded and their main habitat requirements
were presented. The available distributional data were reviewed and proposals made to
complete the surveys and to implement the conservation needs, especially the ones relevant to
the watercourses management office.
In the northern part of the region, most of the rivers and streams are heavily polluted and their
banks damaged. Most of the species concerned by the present report are therefore absent or
scarce. In this region, the priority is a significant reduction of the pollution level. In the south,
water quality is better and the hydraulic works were less strong, except in some limited parts.
Formerly distributed throughout the Ardenne, the pearl mussel is now limited to very few
rivers (Ourthe, Sûre, Semois and Our catchments). Its conservation status is of great concern
since its populations are tiny and made up of old individuals only. The situation of Unio
crassus is better as far as its ecological requirements are less specialised. Some young
individuals were found, indicating that this mussel is still reproducing in several rivers. The
water shrew is present throughout the region whereas the Miller’s water shrew is restricted to
the Ardenne, east of the river Meuse. Their precise habitat requirements are not well known
and it should be interesting to start up a new survey of both species including the study of
their ecology. The few otters still surviving in the south of the region must benefit from
habitat preservation measures. Suitable structures for holts, couches or resting places must be
located (GIS) and protected. The main conservation problem for the kingfisher and for the
sand martin is the protection of banks suitable for nest-building. These structures ought to be
mapped and strictly protected. As far as the dipper and the bats are concerned, some attention
is needed when bridges need maintenance repairs. Small cavities or even nestboxes must be
fit up to allow these animals to breed or to rest.