Background The European mink (Mustela lutreola) used to inhabit the courses and banks of rivers and wetlands in central and northern Europe, but now its distribution is reduced to two small sub-populations. The eastern one, in north-eastern Russia, is rapidly disappearing due to the introduction of a competitor, the American mink (M. vison). The western sub-population, is only found in the south-west of France and northern Spain, where in the last few decades its area of distribution has shrunk by some 70%. At the moment there are only about 800 adults left in an area of 40 000 km2. Experts believe that without urgent action the European mink will disappear over the next decade. The upper Ebro basin (Burgos, Soria, Alava, Rioja and Navarre) is the only region still sustaining a relatively healthy population of this species, chiefly due to the absence of its harmful competitor, the American mink. This project forms part of a coordinated Action Plan between various neighbouring regions, aimed at saving the European mink from extinction in the European Union. Objectives Rioja holds around 40% of the population of the species in Spain. As for the other two projects adopted for this species in Spain this year, the objective of the present LIFE-Nature project is to ensure the long term conservation of the species is safeguarded by eliminating as many of the threats as possible. Thus, steps will be taken to prevent the spread of the American mink in the region. A programme of measures will be implemented to conserve the aquatic environment and the natural riverside vegetation which together form the bulk of the European mink's natural habitat. The project will also aim to control diseases, pollutants and the genetic deterioration of the species. In addition, periodic monitoring will be done to assess the population trends and the effectiveness of the measures carried out.