Management and impact of Invasive Alien Species (IAS) in Lough Erne in Ireland

Map of Lough Erne Case Study and surrounding area. Source: Dr. Tim O'Higgins, University College of Cork
Area characterisation: 

Lough Erne (Fermanagh County, Northern Ireland) is made of two parts, Upper Lough Erne and Lower Lough Erne both of which are widened channels of the River Erne, the second largest river in Ireland.  The former is a shallow, naturally eutrophic lake covering an area of 1,552 ha with a complex shoreline containing many small islands and peninsulas. Lower Lough Erne is a larger deeper lake with an area of 15,303 ha and a maximum depth ca. 60m, the two are joined by a section of the Erne river approximately 10km long.


The AQUACROSSCase Study examines the implications of  invasive alien species regulation for practical management in Lough Erne County (Northern Ireland) in the context of existing environmental commitments under EU legislation. It assesses whether biodiversity and related ecosystem services targets can provide clear environmental management objectives.


The most significant present invasive alien species are the zebra mussel (Dreisenna polymorpha) and the Elodea waterweed (Elodea nutallii). There are many potential desirable management endpoints and many potential management options to reach these endpoints.  However identification of and selection of specific endpoints may involve trade-offs between different primary activities and different components of the ecosystem.  For the management of invasive species and specifically Elodea, physical removal of Elodea is not cost effective nor is artificial shading of the plants to reduce growth. One potential management option which could enable recreational activities is the raising of lake levels during the Summer time, to allow passage of boats over the Elodea (and possibly remove some stands of Eldoea by shading).  This option could require re-negotiation of the intergovernmental agreement on the Lough Erne levels. This option might also be contentious with farmers, as it could involve increased summer inundation of agricultural lands.  Since the Lough Erne area is prone to flooding, any discussion of raising water levels may prove contentious.

Two species, the European Eel and the Atlantic Salmon are the subject of intensive management efforts due to their (historic) commercial importance and dwindling numbers- Salmon for example are a species of least concern, but wild stocks in the Atlantic no longer support commercial fisheries.  The salmon in particular have been the subject of well documented and prolonged management efforts in terms of re-stocking, but for the Erne the rates of return of re-stocked fish have been very low.  This problem is common to many locations where hydroelectricity is located on salmon rivers.  In Lough Erne, a more detailed analysis of the economic value of the hydroelectricity (including the costs of current management efforts for salmon and eel) and the opportunity cost of a healthy salmon fishery in the Erne could favour prioritising recreational salmon fishing over the production of hydroelectricity. 

Potential impacts/benefits: 

Lough Erne sustains multiple competing primary activities each with different requirements from the system in terms of ecosystem services and biophysical abstraction. The Erne Loughs are heavily modified water bodies, and also contain a range of non-native origin with a very long history of introductions.  Balancing the needs of competing uses while also meeting the additional legislative burden of the Invasive Alien Species Directive requires consensus on ecosystem end-points as well as effective cross border cooperation.

Transferability of the result: 

This project is a Case Study under the Horizon 2020 project AQUACROSS, which builds on work undertaken in the previous pillars to develop concepts, practices and tools for better implementation of Ecosystem Based Management. This includes identifying and understanding the linkages between aquatic ecosystems and human well-being and identifying innovative management responses for aquatic ecosystems.

Lessons learned: 

As part of the Horizon 2020 AQUACROSS project, this Case Study seeks to advance the application of Ecosystem Based Management for aquatic ecosystems. AQUACROSS aims to develop and test an assessment framework, which considers the full array of interactions, including human activities, within aquatic ecosystems.