The repopulation of the European eel, a species that has been reduced in the last 25 years due to pollution, the loss or alteration of its habitats or obstacles to its movement in rivers, is one of the priority objectives of the European Council of Ministers, a body that has developed measures aimed at the conservation of this species. To the same end, AZTI-Tecnalia, in collaboration with the Biodiversity Foundation, the Provincial Council of Gipuzkoa and the Basque Water Agency (URA), has developed a reforestation project.

This is a pilot experience on the Oria River, an action carried out in June 2011, which achieved the translocation of more than 2,400 wild eels and eels from the lower course of the river during their migration upstream to Ursuaran. Another of the activities consisted of the release of 6.4 kilograms of elvers collected by the fishermen of the Oria, half of which were reintroduced directly at the height of the town of Zegama, while the other half was released into the Agauntza River after having fattened them at the Mutriku Aquaculture School for a period of two months.

The results of the experience have been very positive, since the specimens have developed a remarkable growth which increases their chances of survival. And after this first experience, the eel translocation will begin this year in the Urola River, and may be extended to the Basque basins and northern Spain.