Background Spain’s Lake of Banyoles is the second largest lake in the Iberian Peninsula. It is a unique Mediterranean wetland, designated as an Natura 2000 network site (SCI), which hosts several valuable EU-listed habitats, some of them priority habitats for conservation. Four species of Community Interest resident in the Estany de Banyoles SCI (ES5120008) have been identified as being at risk and in a critical situation. These are: European pond terrapin (Emys orbicularis), Mediterranean turtle (Mauremys leprosa), Mediterranean barbel (Barbus meridionalis) and Unio elongatulus. Alien fish species, most of which had been introduced to encourage angling, have thrived, and thus the populations of most of the lake’s autochthonous fish species have fallen in numbers – or even disappeared. Thus, the three-spined stickleback (Gasterosteus aculeatus) died out in the area at the beginning of the past century, while the Mediterranean barbel and Squalius laietanus could only be found in a few small streams. Only the freshwater blenny (Salaria fluviatilis) and the European eel (Anguilla anguilla) survived in the lake, albeit in very small numbers. The alien species have also provoked changes in the ecology of the lake, namely, a fall in the water quality of the main and satellite lakes, alterations in underwater plant communities, and a gradual disappearance of autochthonous fauna, above all amphibians and freshwater mussels. In addition, autochthonous species of terrapin have to compete with invasive alien species, as the continuous release of the red-eared slider (Trachemys scripta elegans) in the area over recent years has pushed the local populations of autochthonous terrapins to the brink of extinction. The proximity of streets, gardens and agricultural areas has enabled alien invasive plant species to proliferate around Lake Banyoles. The following species represent the greatest threat: Pyracantha or scarlet firethorn (Pyracantha crenatoserrata), Chinese or glossy privet (Ligustrum lucidum), Japanese honeysuckle (Lonicera japonica), and Cherry plum (Prunus cerasifera). In addition, the giant cane (Arundo donax) is also present in the area. Objectives The main objectives of the PROYECTO ESTANY project were to stabilise species and habitats of Community Interest in the Natura 2000 Network site “Estany de Banyoles”. Actions aimed to control invasive species and strengthen the conservation status of the European pond terrapin (Emys orbicularis), Mediterranean turtle (Mauremys leprosa), Mediterranean barbel (Barbus meridionalis) and Unio elongatulus. Captive breeding and/or restocking with stock from other nearby healthy populations was planned as well as work to restore the quality of priority habitats and/or extending wetland habitats. Results The PROYECTO ESTANY project reached its main objectives, namely combating, slowing down, and reversing the decline of species of Community interest caused by alien species. Over its four-year duration, the project developed and conducted a comprehensive campaign to eradicate invasive alien fauna (fish and terrapins) and flora. The project applied two different strategies. On the one hand, it used a variety of techniques (electric fishing, netting and trapping) in order to control the lake’s main alien fish species, including the large-mouth black bass (Micropterus salmoides), pumpkinseed (Lepomis gibbosus), carp (Cyprinus carpio), European perch (Perca fluviatilis) and zander (Sander lucioperca). The fishing campaigns were designed to be both long and intense enough to have a lasting impact on the invasive fish populations – above all on the large predators (Micropterus salmoides and Sander lucioperca) – in order to provide the lake’s autochthonous species with a chance to recover and restore a balance in the lake’s fish communities. The project successfully improved techniques and methods for controlling alien fish species in a large lake, removing over 100 000 individual fish. This drastically reduced the population density of alien fish species, above all of largemouth black bass (75%) and carp (90%). On the other hand, the project released over 20 000 autochthonous fish (75% Mediterranean barbel) and established new breeding sites for Mediterranean barbel around the lake. It also achieved an increase in the density of host fish of the freshwater mussels (e.g. 95% increase in freshwater blenny). A number of different actions targeted alien invasive terrapins in the lake in order to reduce their populations and strengthen the populations of the endemic European pond terrapin. The project removed about 580 alien terrapins of seven different species from the project areas (achieving an 80% reduction). All 130 native terrapins released during the project’s duration came from the breeding centre Centre de Reproducció de Tortugues de l’Albera, where European pond terrapins have been reared since the 1990s from an original stock of a dozen terrapins from the basin of the river Ter (which includes the Banyoles lake). The released terrapins measured 7–11 cm and had been implanted with a subcutaneous microchip that identified each animal and/or had a radio transmitter attached to their carapace. In this way, the movement of individual terrapins could be studied, along with their adaptation to the habitat, which has been excellent to date. The monitored terrapins show good growth rates (size and weight) and bright colours. They have adapted well to the release sites. 40% of the released specimens were re-captured and the minimum mortality rate was estimated at 4%. What is more, the project confirmed the presence of a small population of the Mediterranean turtle (Mauremys leprosa). Before the beginning of the project, Pyracantha or scarlet firethorn (Pyracantha coccinea), Chinese or glossy privet (Ligustrum lucidum), Japanese honeysuckle (Lonicera japonica), and Cherry plum (Prunus cerasifera) were especially common in two parts of the wetland: around the Estanyol d’Ordis to the north of the main lake, and around Estanyols de la Puda to the south. Eradication works were carried out on private land with the permission of the owners and on public land (12 ha in all). One of the most important actions was the purchase of agricultural land on the right bank of a stream, Riera de Can Morgat (2 750 m2). Here, the giant canes were eliminated, the stream was widened and autochthonous species of riparian plants were planted (400 specimens). In parallel, the project worked to reinforce the freshwater mussel populations. These efforts included a captive breeding programme for freshwater mussels, for which the project set up a specialised laboratory according to established protocols. This essential part of the project achieved extremely good results, rearing of large numbers of juvenile mussels. Work on the installations, which include indoor aquariums and outdoor tanks for fish and mussels, began in February 2010. By spring 2011, 10 000 mussel larvae had been bred thanks to breeding and rearing techniques that improved with time. The installations were initially designed to last just for the length of the project only, but could continue work for a further four years. The project was the first in Europe to successfully breed and rear such a large numbers of juvenile mussels. 132 918 juveniles were born between 2011 and 2013. At the end of the project, 2 622 juveniles between 2 and 1 years old and an estimation of 6 000 juveniles (survivors of the 57 100 born in 2013) are kept in captivity (in the laboratory and in the cages in the lake). High mortality rates during the first days of juvenils life has been observed. After the release of the juvenile mussels (born in 2011 and grown up in the laboratory) into the lake and its associated watercourses, the population of U. mancus increased by at least 40% (release of 278 individuals). The population of U. ravoisieri increased by over 200% (release of 224 individuals). In general, the problem of invasive alien species (IAS) and the negative effects that they have on habitats and autochthonous species is poorly understood by the wider public. Hence, the project conducted a number of different awareness raising actions directed at both local and regional residents as well as at the scientific community and, above all, at schoolchildren. The project consortium applied a variety of strategies including appearances on television and radio and in the printed press as well as giving talks at conferences. The project published didactic material and organised leisure activities in and around the lake. Besides, the website of the Consortium for Lake Banyoles (http://www.estanyespainatural.net) allowed people to find out more about certain areas of the project and the actions carried out there. To create an impact within the scientific and technical community, the project published all of its reports and protocols online and participated in numerous congresses and workshops. Further information on the project can be found in the project's layman report and After-LIFE Conservation Plan (see "Read more" section).