Background Friuli-Venezia Giulia is an Italian region with numerous perennial surface streams and natural lakes. These freshwater habitats host an extremely rich and diversified fauna, including the native white-clawed crayfish (Austropotamobius pallipes) – the country’s most widespread, indigenous crayfish species. The Friuli-Venezia Giulia stock of native crayfish populations, which is particularly important compared with those of other Italian regions, includes some endemic subspecies that represent an important genetic heritage for biodiversity. These regional populations, however, are under serious threat, and may be at risk of local extinction, due to the recent and widespread appearance of a highly invasive, non-native species, the Louisiana red swamp crayfish (Procambarus clarkii). Objectives The RARITY project had two main objectives. Firstly, to combat the spread of the invasive alien crayfish species Procambarus clarkii, which is threatening native crayfish species, biodiversity and even, in some cases, human health; and secondly, to increase populations of the native crayfish species Austropotamobius pallipes. In order to meet these objectives, the project aimed to draw up and implement a Regional Regulation regarding the fishing of crayfish species in Friuli-Venezia Giulia, to promote the conservation of Austropotamobius pallipes and back measures to combat the spread of invasive non-native crayfish. Results The RARITY project successfully contained the spread of the invasive non-native Louisiana red swamp crayfish (Procambarus clarkii) and improving the conservation status of native crayfish populations, in the Friuli Venezia Giulia region, in northern-eastern Italy. A total of 21 500 Procambarus clarkii were captured and removed during the project’s implementation, resulting in the invasive species being eradicated from two sites. Early Detection Rapid Response Protocols for the invasive crayfish were implemented in ten sites. Monitoring was carried out in the whole Friuli Venezia Giulia region for native and non-native crayfish, through a network of 238 monitoring stations, with the involvement of over 60 volunteers (fishermen) linked with the coordinating beneficiary. Data for status, abundance and distribution for all crayfish in the region was collected and analysed. Two farming structures were restored for breeding the native white-clawed crayfish (Austropotamobius pallipes), with a total of 42 126 juveniles produced during the project’s duration. A total of 34 806 crayfish were released in eight Natura 2000 network sites in the Friuli Venezia Giulia region (2012-2014). The project developed and tested three innovative techniques aimed at controlling the invasive Procambarus clarkii, of which two were tested in the field. In particular, the Sterile Male Release Technique was applied in Casette Lake (a closed lake) with positive results. Males were sterilised by X-rays before release. They were able to mate with wild females, in competition with wild males, and this reduced the number of fertile eggs that the females laid. This technique had already been tested in Italy, but the RARITY project enabled the ideal radiation dose to be determined. This technique, combined with intensive trapping, enabled an 87% reduction in the population of the invasive Louisiana red swamp crayfish to be achieved. The project showed how the sterile release technique can be replicated in other sites having characteristics similar to Casette Lake. Another innovative technique involved the produced in the laboratory of baits that included compounds having similar effects to sex pheromones, to attract mature males of the same species during the reproductive period. The sex pheromone mimic was synthesised using a phage library from the RNA of crayfish tissues. This technique was tested in the field and confirmed to be species-specific, so has good potential for the baiting of traps. The third innovative technique (an addition to the original work programme), involving the baiting of food pellets with gonad-inhibiting hormones to reduce fertility, was finalised and tested in the laboratory. Many awareness-raising activities were carried out by the project, using a range of dissemination tools, including a film, a book, brochures, handbooks, noticeboards and newsletters. The project presented its work at numerous public events and reached specialist audiences through scientific conferences, workshops and seminars. All RARITY documents have been made available on the project website, to encourage the replication of the project activities. The project helps to implement a range of global, European and national policy. Internationally, Austropotamobius pallipes was downgraded by the IUCN from the "vulnerable" to the "risk of extinction" category in 2010, while it requires protection under Annex II of the Habitats Directive (92/43/EEC). The project represents good practice in the context of European Regulation 1143/2014 on the introduction and diffusion of invasive alien species. Thanks to the project, a Regional Regulation (no. 27 of 31/12/2012) for the protection of Austropotamobius pallipes was approved and issued. This regulation also prohibits the capture and release of invasive crayfish (penalties ranging from €25 to €500 are foreseen). The coordinating beneficiary is the body responsible for implementing activities aimed at preventing and controlling invasive crayfish. The ‘Action Plan for the protection of white-clawed crayfish’, elaborated by the project after its conclusion, was approved by the Board of the Ente Tutela Pesca Friuli Venezia Giulia in July 2015. The work done with the general public and a range of stakeholders (e.g. anglers, hunting/fishing shops, public administrations, rangers, reclamation consortiums) to increase awareness of invasive species should reduce the damage caused by invasive non-native crayfish, with knock-on socio-economic benefits for the region. Further information on the project can be found in the project's layman report and After-LIFE Conservation Plan (see "Read more" section).