The Grand Canal and Barrow Navigation transverses three different River Basin Districts (Shannon, Eastern and South Eastern) and four major river catchments (Shannon, Boyne, Liffey and Barrow), and passes through a variety of habitat types (e.g. farmlands, bogs and urban areas). It is of significant ecological, conservation and recreational importance. Being part of the navigable waterways network in Ireland, these systems are subject to regular boat traffic and significant usage by a variety of stakeholders (e.g. boaters, anglers and walkers). The River Barrow Navigation is a designated Special Area of Conservation.

Map of the Barrow Navigation

Map of the Barrow Navigation

During the CAISIE Project the impact of AIS on the native ecology of the  Barrow Navigation was assessed. Invasive plants such as Himalayan balsam, Japanese knotweed, New Zealand and Nuttall’s pondweed had a serious negative impact on native plant communites in infested areas, resulting in a notable decrease in native flora and faunal biodiversity. The re‐establishment of native habitat was observed after control measures were implemented in areas infested by each of these species. The high density infestation of Asian clams in the River Barrow below St. Mullin’s (up to 18,000 clams per m2) has substantially altered the structure of river bed and few invertebrate species are now present.   

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. 

 Invasive species along the Barrow navigation:

 

Asian Clam in the Barrow River.

 

Himalayan balsam 

 

Japanese knotweed 

 

Giant hogweed


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