Non–native aquatic invasive species are now an unwelcome feature in many sections of the Grand Canal and Barrow navigation. The abundant growth of some of the invasive plant species can fill the water channel and make conditions difficult for navigation, angling and other water-based pursuits. The aquatic weed control methods operated by Waterways Ireland provide short-term respite for recreational users but it is recognised that longer-term vegetation clearance is a must.
CAISIE (the acronym for ‘the control of Invasive Species and the Restoration of Native Communities in Ireland’) are experimenting with a new and novel weed control method that might offer effective long-term weed control in the canals network with minimal resource input. The method centres on the exclusion of light from the submerged plants using sheets of jute matting. The jute material is made of natural fibre and will biodegrade totally in situ in the aquatic habitat. This method met with considerable success when piloted against a high impact invasive plant species (Curly-leaved waterweed (Lagarosiphon major)) in Lough Corrib and rapidly killed any of the invasive plants that were covered. An added bonus associated with the method is that many native plant species are able to grow through the porous matting once the invasive plant has been killed. For more information see www.caisie.ie.
Two high impact invasive plant species that currently occupy and threaten to substantially expand their range in the canals network are being targeted for the current trials with the jute matting. These are the New Zealand pygmyweed (Crassula helmsii) and Nuttall’s pondweed (Elodea nuttallii). Both of these species have a detrimental effect on the ecological and recreational status of the waterways.
Trials have commenced at four locations on the Grand Canal and Grand Canal Barrow Line, as follows: Limerick Bridge on the Corbally Branch of the Grand Canal; Bord na Mona/Lullymore Briquette factory on the Main Line of the Grand Canal; between the “19th OLD Lock” and Ballyteague Castle on the Barrow Line; and downstream of the 21st Lock on the Barrow Line. Lengths of channel measuring 100 metres have been treated at each location. Each site has been clearly marked on both banksides.
The progress of the trial will be monitored throughout 2011 and into 2012 to assess the efficacy of the weed kill and to ensure that there is no interference to boat traffic or other water use. Boaters are advised to proceed slowly through the trial sections.
