The demolition of a centuries-old dam on the Nivelle River, in France, a few kilometers from the border with Spain, has allowed Atlantic salmon to reach areas of Navarra where their presence has not been recorded, at least since that there are records.
This is great news for this declining species. Thanks to the elimination of dams and weirs that hinder their life cycle between the river and the sea, salmon can access colder and more oxygenated waters, and therefore have more options to survive. Lower flows and increasingly higher water temperatures due to climate change are a threat to the species.
"We have not found the exact date of construction of the dam but we know that it already existed in 1775" and that until the beginning of the 20th century it was used for a flour mill. Subsequently, it fed a stone crusher, the French fishermen's federation that promoted its demolition explained to EFE.
Between 1980 and 2012, it was used to supply a fish farm and since then it has been disused. In 2022, the Pyrénées-Atlantiques Fishing Federation and the National Fishermen's Foundation purchased the facilities to remove the dam and recover the ecological functionality of Nivelle (Ugarana in Spanish), according to the same source.
At five meters high, the infrastructure represented an insurmountable obstacle for all fish species, except for the eel, which could only overcome it under very specific hydrological conditions.
After achieving financial support from the European Open Rivers project, it was demolished in the summer of 2023 and just a few months later, at the end of December, half a dozen salmon specimens arrived in the Urdax area (Navarra) to spawn for the first time. since records exist.
"There is no historical data on the presence of salmon in this part of the basin. It is a joy because the response of the species has been very rapid," stressed the head of the River Environment Section of the Department of Rural Development and Environment. from Navarra, José Ardaiz, who collaborates in the project co-financed with European funds Life Kantauribai, focused on the renaturalization of rivers.
In the last year, the salmon run in the Nivelle basin had been "quite limited", with only 25 specimens counted according to the French colleagues, "and we did not expect the result to be so rapid in this part of the basin", he said. added Ardaiz.
In his opinion, this shows that the salmon "needed to move up" to areas with much better temperature and oxygenation conditions.
Furthermore, it is a good example that when two countries work with the same objective of improving a river, even with different projects, the river responds quickly, according to the expert, who highlighted that in addition to facilitating the passage of fish, Removing dams also releases downstream sediments that are necessary for river life.
Life Kantauribai operates in five basins of the Bay of Biscay: Oria and Urumea, between Navarra and Guipúzcoa; Nive and Nivelle, between Aquitaine (France) and Navarra, and Bidasoa, shared by the three with the main objective of recovering their longitudinal continuity with the elimination of disused dams (25) and the construction of fish passages in those that are not they can demolish (7).
The actions included in this type of projects, he highlighted, focus on dams and weirs that are already in disuse and, in no case, related to the supply of water for human consumption.
What is intended is that salmon and other species, such as burtain, eel or trout, can reach better spawning sites and escape the increase in temperatures and low flows related to the climate crisis.
In recent years, the salmon population has fallen significantly, which has forced fishing to be banned in Navarra in 2023 and 2024, and the situation of the species is quite worrying throughout the Cantabrian coast, according to Ardaiz.
