Background Only a century ago, the European mink (Mustela lutreola) inhabited the rivers, streams and wetlands of a large part of Europe. Currently, its distribution has been restricted to two main sub-populations: the western sub-population in the European Union, which lives in the north of Spain and south-west France and the eastern sub-population in the north-west of Russia, which is rapidly becoming extinct. In only a few decades, the distribution area of the EU population has been reduced by 70% and it is estimated that hardly 800 adult individuals survive. It is now one of the most endangered species on the European continent. As well as habitat deterioration, the main threat the European mink is the massive invasion of the larger and more dominant American mink (Mustela vison), which was introduced into Europe as a result of animals escaping from fur farms. It is also a carrier of Aleutian disease, which could be affecting the European mink population. In Catalonia, viewings of mink are very scarce. From time to time, some are found in the Baix Ebre and Montsià regions, probably from the population settled in the upper part of the River Ebro basin. Objectives This project aimed to contribute to the preservation and expansion of the European mink in Spain and thus avert its extinction in the country. It was to work in Catalonia, which is on the edge of its distribution area, and thus contribute to a broader national Coordinated Action Plan, which has also seen LIFE projects focused on the mink in Castilla y Leon, La Rioja and Alava. The main measure planned was a captive breeding programme. This would serve both to prevent the total extinction of this species in the short-term and enable a reintroduction and recovery programme in the future. It aimed to create a stock of 20 mink in captivity. The best habitats for mink in the region - particularly natural banks and aquatic vegetation - were to be protected to favour a stable population in important areas. Similarly, populations of American mink were to be removed to prevent the settling of this dominant species in the Ebro basin. The project also planned to analyse and monitor: illnesses affecting the species; the effects of contaminating agents; genetic diversity; and the effectiveness of the measures implemented. Results This LIFE Nature project exceeded expectations on captive breeding of the ‘threatened with extinction’ European mink from its western nucleus. Although the project found that the species was now totally absent from the Catalonia region, it successfully prepared the way for its return. The project established new procedures for captive breeding and built, equipped and successfully demonstrated a designated breeding and stocking centre. In the first breeding season, ten original specimens successfully produced 18 cubs. This stock of 28 mink exceeded the original target. Suitable habitats for the reintroduction of the European mink were studied and restored. In particular, barriers to a natural recolonisation from the neighbouring Navarre region were removed and a proposal made for pSCI enlargement. All the important habitats for the species will be in the Natura 2000 network, and protected corridors will ease its dispersive movements. Culling campaigns of American mink were carried out every year in the basin of the Ebro river. These efforts will continue in the future as a network of experts, wardens and stakeholders has been created to do this. Trapping schemes were tested as a means to create areas free of American minks and surveillance on effective methods for eradication continues. The project carried out a genetic study of the mink population, and exhaustive analyses of potential pathologies and pollutants. Data of outstanding value for the conservation of the European mink were gathered in four years of research and monitoring. As well as developing this scientific knowledge, public awareness of the European mink and its survival problems was developed through carefully planned materials and activities.