Background Lough Corrib is an internationally renowned brown trout fishery in western Ireland. It is a Special Area of Conservation (SAC) under the EU Habitats Directive and a Special Protection Area (SPA) under the EU Birds Directive. It incorporates 14 habitats listed on Annex I of the Habitats Directive (notably, “Hard oligo-mesotrophic waters with benthic vegetation of Chara spp.”) and is home a range of Annex II species, including sea lamprey (Petromyzon marinus), Atlantic salmon (Salmo salar), freshwater pearl mussel (Margaritifera margaritifera), white-clawed crayfish (Austropotamobius pallipes) and the lesser horseshoe bat (Rhinolophus hipposideros). The Grand Canal – Barrow Line is a man-made watercourse stretching across Ireland from Dublin to the River Shannon and southwards down to the River Barrow. Taken together, it supports rich and diverse floral and faunal communities, including such Annex II species as the opposite-leaved pondweed (Groenlandia densa), the white-clawed crayfish (Austropotamobius pallipes) and the European river lamprey (Lampetra fluviatilis). However, aquatic invasive species (AIS) have, in recent years, become a major threat to the biodiversity of these ecosystems. They impact both directly and indirectly on habitats and species of Community interest as well as carrying additional risks including exacerbating the impact of flooding events and negatively impacting upon the recreational use of waterways Their adverse impact will continue to increase and spread to other linked water bodies unless effective eradication and control methods are developed. In Lough Corrib, curly-leaved waterweed (Lagarosiphon major) spread rapidly throughout the lake since first appearing in 2005 threatening its ecological integrity (notably the keystone Chara habitat) and conservation status. The shallow character of many areas of this large water body made it highly susceptible to invasion. In the Grand Canal and Barrow Line waterway, three highly invasive plant species Nuttall’s pondweed (Elodea nuttallii), New Zealand pygmyweed (Crassula helmsii) and water fern (Azolla filiculoides) have also become established in recent years. Objectives The overall objective of this LIFE+ Biodiversity project was to contribute to halting the loss of biodiversity in Irish freshwater ecosystems by preventing further impacts on native biodiversity from high impact aquatic invasive species. It specifically aimed to develop and demonstrate new and effective control methods, particularly for submerged aquatic species. Site specific objectives were: The eradication of curly-leaved waterweed from Lough Corrib using a number of methods over three seasons; The prevention of further spread of three AIS by implementing control measures in a key dispersal corridor of the Grand Canal and Barrow Line, including mechanical removal and targeted herbicide application.The project planned to investigate boating as a vector in the spreading of species, quantify the impact on native communities of the removal of invasive species and undertake laboratory testing of potential biological control mechanisms. The project sought to collect data on effective control methods and develop guidelines for effective aquatic invasive species management to be exchanged and disseminated through links with policy makers and similar control teams in other locations. Key additional objectives were around developing an effective programme of stakeholder engagement and awareness-raising. By building capacity on invasive species control and remediation of native biotic communities by transplantation of native species from unimpacted areas, the project hoped to contribute to the protection of biodiversity in Ireland and the European target to halt biodiversity loss by 2020. Results The CAISIE project was completed successfully with significant achievements towards the halting of biodiversity loss in Ireland. Its main achievements included the development and demonstration of effective control methods on highly invasive plant species, a programme of stakeholder engagement, and policy development and dissemination. In Lough Corrib, over 90% of the original 92 ha infestation of curly-leaved waterweed was treated. On the site itself, this managed to bring the weed coverage down to 'manageable levels' - below 10 ha – and prevented its spread to the large lower section of the lake. Monitoring has demonstrated that these methods have facilitated the re-establishment of native species and keystone plant habitats. In addition, previously infested areas have been re-opened for angling, boating and other recreational activities. The project developed new survey methods to monitor the distribution and extent of colonisation by curly-leaved waterweed and to assess the efficacy of the control measures employed to treat it. A herbarium of indigenous aquatic plant flora for Lough Corrib was prepared. The project also established a ‘rapid reaction’ capability to quickly respond to new AIS threats in Lough Corrib. In the Grand Canal and Barrow Navigation project area, great success was achieved with extensive control operations on New Zealand pygmyweed, Japanese knotweed, giant hogweed and Nuttall's pondweed. However, the Asian clam (discovered during the project) and to a lesser extent Himalayan balsam remain a problem in the Barrow Navigation. Benthic barrier, dredging and mechanical disturbance control trials were conducted on the Asian clam with results from the latter two control approaches indicating they may prove to be an effective means of treating dense Asian clam infestations in future. The upstream spread of Himalayan balsam has been contained in the Barrow Navigation as a result of extensive manual removal efforts but it remains intermittently present in this system below Athy town. Until a comprehensive control solution is found for Asian clam and Himalayan balsam, the objective to 'prevent further spread' cannot be said to be yet fully achieved. Looking to the sustainability of achievements, the project has provided a suite of scientifically assessed plant control methods that can be employed on submerged invasive species in other situations. Notably, the pioneering use of jute matting and the development of trailing knives - V-blades - for the control of submerged aquatic weeds has already resulted in it being used in other weed infested waters in Ireland, the Netherlands, UK and further afield. The project made considerable progress towards identification of a suitable biological agent to control curly-leaved waterweed. The dissemination and stakeholder engagement was a great success of the project. Notably, it successfully drew up and circulated bio-security guidelines which have been adopted by stakeholders such as the National Coarse Fishing Federation of Ireland, Irish Angling Development Alliance and Inland Fisheries Ireland. It produced guidelines on effective measures to control a range of high impact AIS and a list of concrete recommendations to inform invasive species policy development, both nationally and internationally. Further information on the project can be found in the project's layman report and After-LIFE Conservation Plan (see "Read more" section).