Background The area targeted by the project is in the ‘Aigüestortes i Estany de Sant Maurici’ National Park, which is a high-mountain landscape (3 000 m – 1 200 m) with impressive relief. It includes the Natura 2000 sites of Alt Pallars and Aigüestortes. Publicly owned land accounts for 98.36% (13 888 ha) of the park and 24.78 % of the Natura 2000 sites. Perhaps the most notable features of the park are its water courses, with close to 200 lakes and countless streams. These provide important aquatic habitats, which cover 1.4% of the surface area of the park and are the main focus of the project. They are particularly important for priority aquatic species, such as Pyrenean desman (Galemys pyrenaicus) and the European otter (Lutra lutra). The national park is also included in the RAMSAR network. However, these aquatic habitats have been impacted by human interference. Some lakes and rivers in the target area have dams and hydroelectric facilities, which were developed before the area was protected. These cause habitat fragmentation and – along with recreational activities – present the greatest threat to the conservation of the park ecosystems. Objectives LIFE LimnoPirineus aims to restore targeted aquatic habitats in the Aigüestortes i Estany de Sant Maurici National Park. The project will restore the ecological functioning of 19 high mountain lakes through the eradication – or significant reduction - of alien invasive fish species. It will establish new populations of targeted amphibian species - Rana temporaria, Alytes obstetricans and Euproctus asper - in the lakes where allochthonous fish have been removed. The project will intervene to protect and restore the quality of peat bogs and tufa-forming springs that are currently under pressure from tourism and livestock. Additional targeted restoration measures will include hydraulic restoration at one site and experimental recuperation of peat bog habitats in an area formerly occupied by a small dam. Other targeted interventions will include: improving the conservation status of the listed habitat, Natural eutrophic lakes and its floating water-plantain (Luronium natans), in the Natura 2000 site at Estanho de Vielha, also targeted by the project; and improving the Cottus gobio population in isolated headwater streams, as well as the establishment of a second population. Finally, the project will create a viable seed bank of significant species of the targeted habitats that will allow the recreation of the habitats in case of strong anthropogenic impacts. Expected results: The complete eradication of allochthonous salmonids - Salmo trutta and Salvelinus fontinalis - in three areas of Aigüestortes; The complete eradication of Phoxinus sp. in two lakes in the Alt Pallars site and a global reduction above 80% in two other sites in Alt Pallars and Aigüestortes; The restoration of the structural quality and ecological functioning of 19 high mountain lakes with the Annex I habitat, Oligotrophic waters containing very few minerals of sandy plains, in six project areas; An improvement in the conservation status of the listed habitat, Natural eutrophic lakes, and the species Alytes obstetricans and Luronium natans in the Natura 2000 site at Estanho de Vielha; An improvement in the conservation status of Galemys pyrenaicus, Lutra lutra, Rhinolophus hipposideros and the Plecotus macrobullaris in Aigüestortes and Alt Pallars; The establishment of new populations of Rana temporaria (approx. density of 10 ind. m-1 of perimeter), Alytes obstetricans (2 ind. m-1) and Euproctus asper (0.05 ind. m-1) in lakes currently occupied by allochthonous fish – providing an overall improvement of these metapopulations; An improvement (in terms of size and genetic diversity) in the population of the isolated Cottus gobio at Aiguamòg and the establishment of a second population at Ruda, with a relative density similar to that of the existing population; A reduction in peat bog degradation due to tourism and the restoration of bog quality over 470m2 at two sites: Molières in Aigüestortes (300 m2); and Plans de Sotllo in Alt Pallars (170 m2); Experimental peat bog restoration at a site formerly occupied by a small dam, which covers over 200m2 at the Font Grossa site (Aigüestortes); Hydraulic restoration of the peat bogs of Trescuro (Aigüestortes), with a recovery of at least 50% of the original inundated surface and the characteristic watering regime; Protection of tufa-forming springs from livestock pressure at Obagas del Montsent de Pallars and Estanyeres, and at Estanho de Vielha, leading to an improvement in the conservation of Petrifying springs with tufa formation habitat; Creation of 40 lots of seeds of 3 000–4 000 units each, representing at least 25 different species needed for the recovery of the targeted listed habitats.