Lough Corrib is a large limestone lake in the west of Ireland. It has recently become home to Lagarosiphon major (distribution maps  of Lagarosiphon major in Lough Corrib 2005-2008 ) and zebra mussels. These invasive aquatic species have caused considerable changes to the ecology of the lake.

Lough Corrib is Ireland’s second largest lake, with a surface area of c. 17,800 hectares. The lake can be topographically divided into three main parts: an upper lake, a relatively narrow middle lake and a shallow lower lake. It is underlain primarily by carboniferous limestone to the east and south, and siliceous rocks to the north. The lake is of considerable ecological and conservation importance. It is designated as a Special Area of Conservation and Special Protection Area, and includes 14 habitats and six species listed in the European Union Habitats Directive. It is internationally renowned as a wild brown trout and Atlantic salmon recreational fishery.

Curly-leaved Waterweed Control on Lough Corrib.

Dredging trials (box, hydraulic and electric) were undertaken in the lower River Barrow Navigation to target the extensive Asian clam populations in this section of the river. Results indicated that this control approach may prove to be an effective means of treating dense Asian clam infestations in future. Benthic barrier trials (using jute matting and plastic sheets with or without rock salt) were conducted on the Asian clam in this watercourse, but were adversely impacted by the strong tidal character of the river and provide no conclusive results.


To have stopped this aggressive invasive weed from colonising and establishing sustainable populations in lower Lough Corrib is a significant achievement as the shallow character of this large water body makes it highly amendable to invasion. A large submerged weed infestation here could exacerbate future flooding events in the Corrib catchment by restricting the normal drainage of water through the system. In addition, it would degrade the current high ecological status of the lower lake. The successful weed control operations undertaken during the Life+ project have reopened previously overgrown areas of the lake for angling and boating.

Moreover, the native charophyte dominated habitat that is vital to maintain a healthy wild brown trout population has been naturally rehabilitated. Indeed, high quality trout and salmon angling has recently been reported in many of these previously infested areas.

Map of Lough Corrib

Map of Lough Corrib

Distribution maps below showing the rapid spread of this invasive weed before dedicated control efforts began.

Fig 1:Distribution of Curly-leaved Waterweed 2005

Fig 2:Distribution of Curly-leaved Waterweed 2006

Fig 3:Distribution of Curly-leaved Waterweed 2007

Fig 4:Distribution of Curly-leaved Waterweed 2008

The graph below displays the success of the control efforts since 2008.

If no action was taken to control this highly invasive plant, 48% of Lough Corrib would become inaccessible. Altering biodiversity and having detrimental effects on Lough Corrib.

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