Ahetze Dam, France

Introduction

The Zirikolatzeko Erreka is a left-bank tributary of the Uhabia River, a small coastal river. The Ahetze Dam was the first obstacle encountered by the fish travelling upstream. This river hosts populations of brown trout, sea lamprey and eel.

Due to the ocean’s proximity, this small barrier presented challenges for migratory fish. The highest stakes are here for the eel (Anguilla anguilla), sea lamprey (Petromyzon marinus) and brown trout (salmo trutta).

Project context and opportunity

In recent years, many pressures have increased on aquatic ecosystems in the project region. River barriers are one of them.  Many projects have recently been carried out on main rivers, but not small tributaries like the Zirikolatzeko Erreka River.

In the context of climate change, the circulation of fish (and of all aquatic organisms in general) is becoming an increasing issue. For these reasons, Federation Peche 64 was in dialogue with the owner of the barrier who no longer used the barrier, and he was in favour of removing it.

Project aims

The project removed the dam and returned the river to its natural bed, opening up 3 km of river, and reconnecting the Zirikolatzeko Erreka river to the main river, the Uhabia River. Sea lamprey and trout spawners will be able to access the upstream spawning grounds, and eels will also be able to colonise new territories. In summary, this project will restore the ecological functions of the Zirikolatzeko Erreka River.

Project achievements

The project concluded successfully on September 19, 2022, following the dam removal. As a result, a stretch of 3 km along the Zirikolatzeko Erreka River has been reopened, providing unimpeded access from the ocean. This development is particularly advantageous for brown trout, sea lamprey, and eel populations.