Benefits of the removal
Maisons-Rouges, 10 years after removal.
© Roberto Epple – ERN France
The shads very rapidly benefited from the removal of the dam : 433 shads were caught in the river Vienne in Châtellerault, about 20 km upstream of Maisons-Rouges (i.e. 91 from the fish pass and 342 from a fish removal operation ; 156 fish were released upstream of the dam) ; and 15 on the Creuse river downstream of Descartes, about 12 km upstream from Maisons-Rouges.
Active spawning sites were observed on the Vienne river in Châtellerault and on the Creuse river l’Ilette. Lampreys were observed on the Vienne river down-stream of the Châtellerault dam, and consequently a new population of lampreys re-colonised the Creuse river up to Saint-Gaultier, the Gartempe river up to Saulgé and the Anglin up to Cancrenier. The presence in July, 1999 of a living salmon, 88 cm long and weighing 4,8 kg, in the Gartempe river at Châteauponsac in the Haute-Vienne department is a very encouraging sign.
No living salmon had been observed so far upstream since the 1920s, when the Maisons-Rouges dam was built. The symbolic return of the salmon, after that of the shads and lampreys which was observed last winter, confirms the positive effects of the removal of the Maisons-Rouges dam on migratory fishes.
The Chinon University is monitoring this experiment. The first results show that the river bed is dynamically coming back to its initial state.
The 10 year monitoring programme instigated by the Chinon University in 2007 has followed the exceptionally positive increase in migrating fish populations.
Here a few statistics: From 2004 to 2007 an automatic counting station on the Vienne, 20 kilometres above the Maison Rouge, registered 3,500 to 9,500 allis shad, 8,300 to 41,600 sea lamprey, 2-12 brown trout and 2 to 11 adult wild salmon.
Alone in the Creuse in 2007 around 9,000 allis shad, 51,000 sea lamprey, 4 brown trout, 60 salmon were sighted swimming past a camera in Descartes 12 kilometres beyond Maison Rouge.
The demolition of the dam has been an undoubted success. This efficient approach for migratory fish has also shown a huge reduction in the sedimentary deficit in the course of the Vienne, with benefits extending even into the Loire.