Eradication of a Highly Invasive Weed in the Grand Canal

Press Release 16th November 2011

New Zealand Pygmyweed (Crassula helmsii)is an aggressive alien invasive weed that was introduced to Ireland as an ornamental species for use in the horticulture trade. It can grow submerged in up to 2 m water depth but is also capable of growing out of water.
It can grow luxuriantly when it is introduced to suitable habitats and will rapidly overgrow all native plant species, thus significantly reducing biodiversity. Its dense vegetation will choke the water column and make it impossible for fish to move about normally. The thick weed will also clog the propellers of boats while also obstructing angling.

Currently, the New Zealand Pygmyweed is relatively restricted in its distribution within the Grand Canal and is only recorded between Kilpatrick and Ticknevin Bridges, a distance of circa 2.2 km. Such is the invasiveness of this high priority invasive weed, however, that it will rapidly spread within the canal corridor and overgrow many miles of channel.

The New Zealand Pygmyweedis named in the Third Schedule of the new Birds and Natural Habitats Regulations (2011) as a non-native species that is subject to restrictions under Regulations 49 and 50. These Regulations were only signed into law in October 2011. Under these Regulations it is an offence to release or allow to escape, to plant, disperse or allow or cause to disperse, to breed, propagate, import, transport, sell or advertise any of the species included in this black list, save in accordance with a licence granted under paragraph (7) of Regulation 49.

IFI made Waterways Ireland aware of the presence of this invasive species in their canal and of the risks that it posed to native biodiversity, water movement and recreational exploitation in this ecosystem. They immediately resolved to make every effort to eradicate the weed and its associated risks. IFI scientists worked closely with WI engineers and a plan to remove the weed was developed. This will get underway in the coming days.

The following schedule of activities has been organised to ensure the safe removal of the New Zealand Pygmyweed from the canal:

Week commencing 14th November – WI will place earthen dams at Kilpatrick and Ticknevin Bridges. This will confine the length of canal in which the Pygmyweed is currently resident. These should be in place by 18th November.
Weed commencing 21st November – WI will lower water levels within the confined section by pumping and IFI will start the process of fish removal. All fish within the section must be electric fished and relocated to the canal beyond the dams. It is likely that many thousands of fish will be removed. This operation will probably take 5 full days.
Week commencing 28th November – WI will pump out the water from the confined section of canal and leave the channel to dry.
Week commencing 5th December – IFI will use an approved herbicide and adjuvant to chemically treat the invasive weed in the dewatered channel (weather dependant). This operation should take 3 days.
On 21st December WI will remove the dams and rewater the channel.

The success of the operation will be monitored throughout 2012 by IFI scientists.

...Ends…

Media Enquiries:

Suzanne Campion
Head of Business Development
Inland Fisheries Ireland
Anglesea Street,
Clonmel, Co. Tipperary.
Tel: 052 6180055 Fax: 052 6123971
Email: suzanne.campion@fisheriesireland.ie Website: www.fisheriesireland.ie

Notes to Editor

Inland Fisheries Ireland is a statutory body operating under the aegis of the Department of Communications, Energy and Natural Resources and was established under the Fisheries Act on 1st July 2010. Its principal function is the protection and conservation of the inland fisheries resource. IFI will promote, support, facilitate and advise the Minister on, the conservation, protection, management, development and improvement of inland fisheries, including sea angling and develop and advise the Minister on policy and national strategies relating to inland fisheries and sea angling.
CAISIE ( is the acronym for ‘the control of aquatic invasive species and the restoration of natural communities in Ireland’). CAISIE is an Inland Fisheries Ireland EU Life+ funded project and is co-financed by the National Parks and Wildlife Service.

For information on New Zealand Pygmyweed please see http://www.fisheriesireland.ie/Invasive-species-list/new-zealand-pigmyweed.html