This project aims to restore free ecological continuity on the Marzes stream, a headwater stream in good ecological condition.
The Marzes watershed includes four mountain streams characteristic of the Massif Central, dominated by salmonid populations: the Marzes stream and its three tributaries. The main channel originates at 1,190 metres near the Col de Légal.
The Marzes stream hosts a multispecies fish community in its lower section and a naturally monospecific population of brown trout (Salmo trutta fario) in its middle and upper reaches. Its main tributary is also inhabited solely by this species.
The stream maintains a significant discharge even during low-flow periods, with low water temperatures suitable for brown trout, making it a critical source of flow support for the Doire River, which is frequently affected by drying events. The Marzes watershed serves as a climate refuge, enabling the complete life cycle of brown trout – a species particularly sensitive to climate change. Its preservation is therefore of major ecological importance.
| Project status | Live |
|---|---|
| Project type | Dam removal: demolition |
| Country | France |
| River | Marzes |
| Removal date | August 2025 and Summer 2026 |
| Km to be opened | 7.5 km |
| Focal species | Brown trout |
| Organisation | Fédération Départementale du Cantal pour la Pêche et la Protection du Milieu Aquatique |
This project is part of the departmental strategy for protected areas in Cantal department. The Marzes catchment area has been identified as an environment with high long-term conservation potential. It is a high-altitude basin with a cool water temperature and an endemic population of brown trout in very good condition. In this context, a complete diagnosis was carried out on the Marzes stream catchment area, with each watercourse in the catchment area surveyed and all obstacles to flow inventoried.
Anthropogenic structures were characterised using the ICE (information on ecological continuity) protocol to assess fish passage in upstream migration. Five obstacles located in the middle/downstream part of the basin have been identified as impassable or severely limiting for brown trout. The Fédération Départementale du Cantal pour la Pêche et la Protection du Milieu Aquatique has therefore decided to continue the project by restoring ecological continuity on the Marzes river.
The project goal is to achieve a total removal of the five targeted barriers and restore ecological continuity over 90% of the distribution area of brown trout in the Marzes stream watershed. Allow fish to move freely during reproduction in order to improve recruitment and population dynamics, but also during very hot summer periods to allow fish to move freely toward areas with lower temperatures (spring-fed zones, confluences, more heavily shaded areas, etc.) and improve the resilience of this healthy environment. This work will help to maintain the Marzes river as a healthy environment in the long term in a context of climate warming.
Another objective is also to reuse materials from the removed structures to stabilise the banks and create high-quality fish habitats at the current location of the structures. The overall goal is therefore to enhance the resilience capacity of the brown trout population present in this watercourse and to ensure its long-term preservation.
This project will also engage with the local community, highlighting the significance of the Marzes stream and its population of brown trout.
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