Removing barriers and creating fish passages stabilizes the breeding salmon population.
Madrid, June 20 (EFE).- Improving the river's longitudinal continuity, through measures such as removing obsolete dams and weirs and constructing fish passages in those still in use, has helped stabilize the number of breeding salmon in the Bidasoa at around 300 per year.
This is the conclusion of a scientific study promoted by the EU-funded LIFE Kantauribai project, which analyzes the evolution of salmon populations in the Bidasoa River over the past 30 years and has been published on the Wiley Online Library platform of the academic and scientific publisher Wiley.
The work was carried out by researchers from the Applied Ecohydraulics Group at the University of Valladolid and technicians from the Government of Navarre and the public environmental management company Orekan (formerly GAN-NIK).
After reviewing three decades of data, the authors of the paper consider it essential to continue implementing measures aimed at restoring the longitudinal continuity of the rivers, as well as protective actions during downstream migration, to ensure the survival and conservation of salmon and the rest of the species that inhabit the Bidasoa.
Furthermore, they have identified other factors that influence the long-term sustainability of populations, such as fishing pressure focused on multi-winter females (primary breeders) and global warming, which influences the availability of food and shelter during their marine and river phases.
Despite everything, researchers are optimistic about the species' continued existence in the Bidasoa River basin.
Life Kantauribai operates in five basins in the Bay of Biscay: Oria and Urumea, between Navarre and Guipúzcoa; Nive and Nivelle, between Aquitaine and Navarre; and Bidasoa, shared by all three. The goal is to improve their condition by restoring longitudinal continuity by eliminating obstacles.
The project is expected to remove 25 disused dams, weirs, and fords, and equip another 7 still in use with fish passages.
Furthermore, it has deployed a comprehensive technological effort in the Bidasoa River to understand how river barriers affect salmon both as they travel upstream and as they descend to the sea, given the suspicion that many end up dying in the canals or turbines of hydroelectric plants. EFEverde
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