Conservation of the Rhone apron: a review of the measures taken to restore the connectivity of watercourses

Abstract

Since the first conservation project in 1998, river fragmentation has been identified as one of the main causes of the decline of Zingel asper, an endemic species of the Rhône river. A number of actions were started in order to restore ecological connectivity in watercourses where apron were still present. Different solutions were implemented, from the construction of fish passes to dam removal, including gate opening during floods for sediment and fish downstream migration. Population monitoring showed significant results with the expansion of the species distribution, either upstream and downstream (Ardèche), or only downstream (Durance). At 240 km at the end of the 1990's, the range of the apron's distribution reached 365 km in 2017. Other measures contributed to this success, such as water quality improvement, a ban on gravel exploitation in riverbeds at the end of the 1990's and a doubling in legal minimum flows downstream of dams in 2014. Despite this progress, socio-economic issues still limit actions identified to secure the distribution range of the species, especially given climate change risks.