What is ‘special’ about Llyn Traffwll SSSI?

Llyn Traffwll has two special features:

As well as the features listed above, Llyn Traffwll has other habitats that contribute to the special interest. These include areas of marshy grassland, marginal swamp, willow scrub and the outflow stream at the southern end of the lake. This mixture of habitats is important for a range of wildlife, such as otters and water vole various insect species (including dragonflies and damselflies) and nesting birds. Unless specified below, management of this site should aim to look after these habitats and species as well as the listed features of interest.

What do we want Llyn Traffwll to look like?

The site should continue to support a clear-water aquatic plant community characterised by a wide variety of submerged plants, while the lakes persist. Water levels and quality should support a characteristic range of water plant species including lesser pondweed and spiked water-milfoil and rare and uncommon water plants such as eight-stamened waterwort and flowering rush. The lake should support a natural and sustainable fish population. Mammals including water vole and otter should be present. There should be fringing reedswamp and fen and some areas of willow carr. They should provide habitat for breeding and wintering wildfowl (including shoveler) and bittern. The mixture of lakes, ponds, ditches and other water habitats; together with the reedbeds, marshland, scrub and wet grassland, should demonstrate the process of natural succession from open water to marshy grassland.

What management is needed on Llyn Traffwll SSSI and why?

Although Llyn Traffwll 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 many factors that could damage the special features at Llyn Traffwll if they are not properly managed. These are the ones we regard as most important:

Water levels: Water levels, essential for the wildlife interest of the site, are controlled by the sluice on the outfall stream. Maintenance of this structure must ensure adequate levels on the lake. Activities (including extraction or diversion of water) which reduce the water supply to the lake should be avoided.

Water quality: Excess plant nutrients (particularly phosphorus and nitrogen) can have an adverse effect on the lake and its wildlife, enabling growth of a narrow range of competitive plant species at the expense of the diversity of desired species. Nutrients may also promote algal “blooms” , which can smother natural plant populations and may de-oxygenate the water (leading to fish-kills). In such circumstances a lake can become persistently dominated by algae with the loss of most other plants and animals. An increase in nutrient levels (eg phosphates and nitrates) may also result in an increased growth of species such as bulrush at the expense of less vigorous species of greater conservation interest. Artificial inputs of nutrients and pollutants should therefore be minimised or preferably eliminated. Care should be taken to minimise applications of herbicides, pesticides, or fertilisers of any kind (including artificial fertilisers, slurry, manure and abattoir or creamery waste) in the catchment, particularly within 10m of the site or any inflow streams. Farmyard drainage must not flow into the lake and sewage or septic tank discharges should be minimised. There should also be no supplementary feeding of stock or dumping, spreading or storage of materials such as manure or silage bales on or adjacent to the SSSI. Livestock should have only limited (watering) access to the lake, to reduce waste inputs and sediment disturbance.

Fisheries and angling: Artificial stocking of the site (including Llyn Astra, which has been used for angling) with any fish (particularly coarse fish) has the potential to destabilise the ecological balance of the lake, for instance by altering plankton grazing or invertebrate or fish predation rates or by sediment disturbance. Any proposals for fish stocking need to be carefully assessed in terms of the potential impact on the ecology and water quality of the lake. Any works associated with fishing eg. fishing platforms or cutting of vegetation need to be designed to minimise the impact on the site and assessed by CCW. If fishing occurs it should be based on natural fish populations and consideration should be given to enable this through appropriate habitat (including stream) management.

Grazing: Uncontrolled grazing damages lake vegetation if stock have access to the much of the lakeshore. Heavy trampling of submerged and marginal plants causes direct damage and raises sediments which, along with animal wastes, may increase water turbidity. Light grazing is required to maintain areas of marshy grassland, preventing a build up of plant debris, controlling scrub and encouraging a wide range of flowering plants. Cattle or ponies are generally the most appropriate stock for such areas. Stocking levels should be determined by the carrying capacity of the land and no supplementary feed should be provided. No drainage or reseeding should be carried out within the marshy grassland.

Scrub: Willow or alder scrub can be very rich in invertebrates and has a role in providing nesting and foraging areas for some wetland birds. However, its extent should be monitored against other desired wetland habitat and occasional control may be necessary.

Invasive non-native species: Plants such as water fern, Australian swamp stonecrop or Japanese knotweed can spread extremely rapidly and out-compete native plants. These species are present on Anglesey, spread by root fragment, fronds or other plant material and are very hard to control. Any equipment, including machinery, fishing tackle, boots, waders and especially wheeled vehicles brought on site should be thoroughly cleaned beforehand, regardless of whether they have knowingly been in contact with any invasive species. Consideration should be given to eradicate any accidental introductions as soon as possible.

Public access: Any significant increases in public access to the site would need to be assessed in terms of its potential to impact on bird populations and plants.


Our knowledge of wildlife is far from complete. It is possible that new features of value may appear and new management 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

Llys y Bont,

Ffordd y Parc,

Parc Menai,


Gwynedd, LL57 4BN,

Telephone: 01248 672500

Fax: 01248 679259