What is ‘special’ about Llyn Garreglwyd SSSI?

Llyn Garreglwyd has one special feature:.

Reedbed is a scarce habitat that is often artificially modified. This is one of the largest reedbeds on Anglesey and is an important habitat for birds such as reed bunting and bittern. The latter has been recorded on site but has not bred in recent years. As well as the reedbed, Llyn Garreglwyd has other habitats that contribute to the special interest. These include fen, marshy grassland, open water and scrub. This mixture of habitats is important for much of the wildlife including a large winter roost of starlings in the reedbed and these too are key components of the special interest of the site. Unless specified below, management of this site should aim to look after these habitats as well as the listed features of interest.

What do we want Llyn Garreglwyd to look like?

Llyn Garreglwyd should include at least 5 hectares of reedbed dominated by common reed, broken up by water channels and small pools. Small patches of trees and scrub should be present around margins of the site, covering no more than 5% of the site in total, but should not form large woodland areas. Areas of fen and marshy grassland to the south-west of the site should support the uncommon geater spearwort.

What management is needed on Llyn Garreglwyd SSSI and why?

Although Llyn Garreglwyd is an excellent place for wildlife it will only remain so if the necessary management continues. CCW’s aim is to work with you to ensure that this management is carried out.

What does this mean in practice?

There are a number of different factors that could damage the special features at Llyn Garreglwyd if they are not properly managed. These are the ones we regard as most important:

Nutrient levels: The vegetation of this site is dependent on a water supply with only moderate levels of nutrients such as nitrates and phosphates. Increased nutrient levels such as agricultural fertiliser runoff or wildfowl may lead to increased growth of species such as bulrush, which may out-compete more desirable species such as common reed and greater spearwort. There should be no increase in duck rearing since they contribute a significant nutrient input to the site.

Water quantity – levels and extent: Wetland vegetation is dependent on a continuing high water table. However, at least part of the reedbed at Garreglwyd appears to be floating, so this part at least is not sensitive to small changes in water level. Any work that reduces inputs to, or increases outputs from, the site has the potential to damage the site. The sluice below Carreglwyd House lake supports the entire system. Should this fail much of the SSSI would dry out and lose its special interest. The sluice should therefore be maintained or if necessary, replaced.

Within the reedbed, areas of open water and firebreaks should be maintained by regular cutting or mowing. Up to 2.5 ha open water could be created to the southwest of the reedbed, by excavation of areas of bulrush, and marginal areas of reedbed. Spoil should be disposed of off site or on areas of higher ground. Details must be consented by CCW.

Grazing: Peripheral areas south of the reedbed are currently grazed under an ESA agreement together with adjacent fields. This prevents scrub establishment and helps to maintain fen vegetation. Stock should not be allowed access to the reedbed.

Burning: Controlled burning of reed is used to “clean” commercial reedbeds. Although extensive or frequent fire has the potential to decimate invertebrate populations of importance to bird life, occasional controlled burns in late winter will reduce litter build-up and scorch invasive willow scrub.

Scrub development and natural succession: Natural processes will gradually infill the site with silt and peat. Willow scrub will invade and develop carr woodland despite work in recent years to control it. The period of reedbed dominance may be extended by willow removal, controlled burning and channel excavation but without major efforts to re-excavate the lake, much of the site will naturally become a wet woodland.

Invasive species: Plants such as water fern Azolla filiculoides, swamp stonecrop Crassula helmsii or Japanese knotweed Fallopia japonica can spread extremely rapidly and out-compete native species. These species are present on Anglesey and could be introduced by root fragment, fronds or other plant material. Any equipment, including machinery, fishing tackle and even boots and waders, brought on site should be thoroughly cleaned beforehand, regardless of whether they have been in contact with any invasive species. Measures should be taken to eradicate any accidental introductions as soon as possible.

Finally: Our knowledge of wildlife is far from complete. It is possible that new issues may arise in the future, whilst other issues may disappear. This statement is written with the best information we have now, but may have to change in the future as our understanding improves. Any information you can provide on the wildlife of your site, its management and its conservation would be much appreciated.

If you would like to discuss any aspect of your SSSI, or have any concerns about your SSSI, please contact your local CCW office.

Your local office is;

Cyngor Cefn Gwlad Cymru/Countryside Council for Wales

North Region

Llys y Bont,

Ffordd y Parc,

Parc Menai,


Gwynedd, LL57 4BN,

Telephone: 01248 672500 Fax: 01248 679259