Afon Ddu

Site of Special Scientific Interest · 52.9588, -4.1556

Open in the interactive map →

Also within

Gwynedd County Eryri / Snowdonia National Park

Climate exposure

This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.

Peatland

Peat habitats store centuries of carbon and depend on a stable, waterlogged water table. Warmer, drier summers dry out peat, making it far more vulnerable to wildfire and to carbon release — a pressure that can undo years of restoration work regardless of how well the site is otherwise managed.

Habitats

Fast flowing river and stream, Lowland wet heath, Upland wet heath

Geology & landscape

Landscape processes: Peatland / Mire

Birds & fish recorded

Fish

SpeciesSeason
Atlantic salmon Spawning
Sea trout Spawning
Sea trout Unknown

Description

Description The Afon Ddu is of special interest for its population of the freshwater pearl mussel Margaritifera margaritifera. It is a small upland catchment in the hills above Garndolbenmaen. The site includes Llyn Du and the river for 3km downstream to include the sections supporting the pearl mussels. Below the site, the river converges with the Afon Henwy to become a tributary of the Afon Dwyfor. The site ranges in altitude from 210m to 140m. This freshwater pearl mussel population is important as the species has disappeared from most Welsh rivers and where the species has managed to persist, most populations are thought to be non-breeding relicts. The Afon Ddu freshwater pearl mussel population is one of the few remaining breeding populations of this species in Wales. The freshwater pearl mussel is dependent on the local salmonid (salmon and trout) populations because its larval stage is parasitic on their gills. Sea trout Salmo trutta trutta spawn in the river and native brown trout Salmo trutta fario are abundant. Otter Lutra lutra and water vole Arvicola amphibius have been recorded in the Afon Ddu catchment. There are areas of botanically interesting mire and wet heath adjacent to parts of the river and around Llyn Du which are also important in providing a protective buffer to the river channel and the mussels therein. Remarks The site is within the Snowdonia National Park. The freshwater pearl mussel is listed under: Annex II of the EC Habitats Directive (Directive 92/43/EEC on the Conservation of Natural Habitats and Wild Flora and Fauna). The freshwater pearl mussel is listed as Endangered (Category 1) on the IUCN Red List, is listed on Schedule 5 of the Wildlife and Countryside Act 1981 (as amended), on Appendix II of the Bern Convention, on the S42 list under the NERC Act (2006) and is also a UK Biodiversity Action Plan 'Priority Species' The following UK BAP habitats are found within the site: Upland heathland, Rivers, Upland flushes, fens and swamps. The following additional UK BAP species are found within the site: Arvicola amphibius(formerlyterrestris)watervole,Lutra lutra Europeanotter,Salmo trutta brown/sea trout

Species mentioned

English name
search for this in other sites		 Latin name
search with Google		 IUCN / Red List Type Family
freshwater pearl mussel Margaritifera margaritifera Not listed in GB list bivalve margaritiferidae
otter Lutra lutra LC carnivore mustelidae
brown trout Salmo trutta LC fish salmonidae
sea trout Salmo trutta trutta Not listed in GB list fish salmonidae
water vole Arvicola amphibius EN rodent cricetidae

Plant communities

A9 — Fast flowing river and stream, Marginal and inundation, Pond ditch and canal, Sluggish river and stream

Potamogeton natans community

Schoenoplectus lacustris, Juncus bulbosus, Sparganium angustifolium, Sparganium erectum, Sparganium minimum, Alisma plantago-aquatica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Elodea canadensis, Lemna minor, Lemna trisulca, Nymphaea alba, Callitriche platycarpa, Callitriche stagnalis, Littorella uniflora, Potamogeton natans, Ranunculus trichophyllus, Glyceria fluitans, Chara subspinosa

A14 — Fast flowing river and stream

Myriophyllum alterniflorum community

Isolepis fluitans, Juncus bulbosus, Fontinalis antipyretica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Lemna minor, Callitriche stagnalis, Littorella uniflora, Potamogeton filiformis, Potamogeton gramineus, Potamogeton natans, Ranunculus peltatus, Chara spp., Nitella hyalina

A17 — Chalk river and stream, Fast flowing river and stream

Ranunculus penicillatus ssp. pseudofluitans community

Berula erecta, Nasturtium officinale, Elodea canadensis, Lemna minor, Callitriche stagnalis, Veronica beccabunga, Polygonum amphibium, Polygonum hydropiper, Potamogeton crispus, Potamogeton pectinatus, Ranunculus penicillatus ssp. pseudofluitans

A18 — Fast flowing river and stream

Ranunculus fluitans community

Fontinalis antipyretica, Fontinalis squamosa var. curnowii, Myriophyllum alterniflorum, Myriophyllum spicatum, Elodea canadensis, Mentha aquatica, Lemna gibba, Lemna minor, Potamogeton perfoliatus, Ranunculus fluitans, Glyceria fluitans, Phalaris arundinacea

H3 — Lowland dry heath, Lowland wet heath

Ulex minor-Agrostis curtisii heath

Quercus robur, Calluna vulgaris, Erica ciliaris, Erica cinerea, Erica tetralix, Ulex europaeus, Ulex minor, Carex pilulifera, Schoenus nigricans, Campylopus brevipilus, Campylopus flexuosus, Leucobryum glaucum, Hypnum jutlandicum, Polytrichum juniperinum, Kurzia spp., Hypogymnia physodes, Cladonia arbuscula, Cladonia coccifera, Cladonia crispata, Cladonia floerkeana, Cladonia impexa, Cladonia pyxidata, Cladonia uncialis, Cuscuta epithymum, Hypericum pulchrum, Polygala serpyllifolia, Potentilla erecta, Viola lactea, Agrostis curtisii, Danthonia decumbens, Molinia caerulea, Pteridium aquilinum, Zygogonium ericetorum

H4 — Lowland dry heath, Lowland wet heath, Upland dry heath

Ulex gallii-Agrostis curtisii heath

Salix repens, Calluna vulgaris, Erica ciliaris, Erica cinerea, Erica tetralix, Erica vagans, Vaccinium myrtillus, Ulex gallii, Carex binervis, Carex flacca, Carex montana, Carex panicea, Carex pilulifera, Trichophorum cespitosum, Juncus squarrosus, Luzula multiflora, Pohlia nutans, Campylopus flexuosus, Campylopus introflexus, Dicranum scoparium, Leucobryum glaucum, Racomitrium lanuginosum, Hypnum cupressiforme, Pleurozium schreberi, Pseudoscleropodium purum, Rhytidiadelphus squarrosus, Polytrichum juniperinum, Calypogeia fissa, Calypogeia muelleriana, Cephalozia bicuspidata, Diplophyllum albicans, Lophocolea bidentata, Hypogymnia physodes, Cladonia arbuscula, Cladonia chlorophaea, Cladonia coccifera, Cladonia crispata, Cladonia fimbriata, Cladonia floerkeana, Cladonia furcata, Cladonia impexa, Cladonia subcervicornis, Cladonia uncialis, Cuscuta epithymum, Lotus corniculatus, Thymus praecox, Pedicularis sylvatica, Polygala serpyllifolia, Polygala vulgaris, Potentilla erecta, Galium saxatile, Viola lactea, Agrostis canina, Agrostis capillaris, Agrostis curtisii, Anthoxanthum odoratum, Danthonia decumbens, Deschampsia flexuosa, Festuca ovina, Festuca rubra, Molinia caerulea, Nardus stricta, Pteridium aquilinum

H5 — Lowland wet heath

Erica vagans-Schoenus nigricans heath

Salix repens, Calluna vulgaris, Erica cinerea, Erica tetralix, Erica vagans, Ulex europaeus, Ulex gallii, Carex flacca, Carex hostiana, Carex panicea, Carex pulicaris, Eriophorum angustifolium, Schoenus nigricans, Eleocharis multicaulis, Juncus acutiflorus, Juncus maritimus, Fissidens adianthoides, Kindbergia praelonga, Scorpidium scorpioides, Calypogeia fissa, Riccardia multifida, Angelica sylvestris, Eupatorium cannabinum, Serratula tinctoria, Succisa pratensis, Drosera rotundifolia, Genista anglica, Hypericum pulchrum, Scutellaria minor, Thymus praecox, Pinguicula lusitanica, Linum catharticum, Dactylorhiza incarnata, Dactylorhiza maculata, Gymnadenia conopsea, Platanthera bifolia, Pedicularis sylvatica, Plantago maritima, Polygala vulgaris, Anagallis tenella, Potentilla erecta, Sanguisorba officinalis, Galium uliginosum, Agrostis curtisii, Agrostis vinealis, Danthonia decumbens, Festuca ovina, Molinia caerulea, Phragmites australis, Chara curta

M14 — Lowland dry heath, Upland wet heath

Schoenus nigricans-Narthecium ossifragum mire

Pinus sylvestris, Calluna vulgaris, Erica tetralix, Myrica gale, Ulex gallii, Carex panicea, Eriophorum angustifolium, Rhynchospora alba, Schoenus nigricans, Eleocharis multicaulis, Juncus acutiflorus, Juncus bulbosus, Ctenidium molluscum, Hypnum jutlandicum, Scorpidium revolvens, Scorpidium scorpioides, Sphagnum auriculatum, Sphagnum palustre, Sphagnum papillosum, Sphagnum subnitens, Sphagnum tenellum, Calypogeia fissa, Kurzia pauciflora, Ordontoschisma sphagni, Aneura pinguis, Riccardia multifida, Drosera intermedia, Drosera rotundifolia, Pinguicula lusitanica, Narthecium ossifragum, Pedicularis sylvatica, Polygala serpyllifolia, Anagallis tenella, Potentilla erecta, Molinia caerulea

M15 — Blanket bog, Raised bog, Upland wet heath

Scirpus cespitosus-Erica tetralix wet heath

Empetrum nigrum subsp.nigrum, Calluna vulgaris, Erica cinerea, Erica tetralix, Myrica gale, Vaccinium myrtillus, Carex binervis, Carex demissa, Carex dioica, Carex echinata, Carex nigra, Carex panicea, Carex pilulifera, Carex pulicaris, Eriophorum angustifolium, Eriophorum vaginatum, Schoenus nigricans, Trichophorum cespitosum, Juncus acutiflorus, Juncus articulatus, Juncus bulbosus, Juncus conglomeratus, Juncus effusus, Juncus squarrosus, Luzula multiflora, Huperzia selago, Selaginella selaginoides, Aulacomnium palustre, Breutelia chrysocoma, Pohlia nutans, Campylopus atrovirens, Campylopus flexuosus, Dicranum scoparium, Leucobryum glaucum, Racomitrium lanuginosum, Hylocomium splendens, Hypnum cupressiforme, Hypnum jutlandicum, Plagiothecium undulatum, Pleurozium schreberi, Rhytidiadelphus loreus, Rhytidiadelphus squarrosus, Scorpidium revolvens, Scorpidium scorpioides, Polytrichum commune, Sphagnum auriculatum, Sphagnum capillifolium, Sphagnum compactum, Sphagnum fallax, Sphagnum palustre, Sphagnum papillosum, Sphagnum subnitens, Sphagnum tenellum, Calypogeia fissa, Calypogeia muelleriana, Diplophyllum albicans, Lophozia ventricosa, Ordontoschisma sphagni, Pleurozia purpurea, Aneura pinguis, Cladonia arbuscula, Cladonia chlorophaea, Cladonia coccifera, Cladonia impexa, Cladonia uncialis, Succisa pratensis, Drosera anglica, Drosera rotundifolia, Hypericum pulchrum, Triglochin palustre, Pinguicula vulgaris, Menyanthes trifoliata, Narthecium ossifragum, Dactylorhiza maculata, Euphrasia officinalis, Pedicularis palustris, Pedicularis sylvatica, Polygala serpyllifolia, Trientalis europaea, Potentilla erecta, Galium saxatile, Viola palustris, Agrostis canina, Agrostis capillaris, Agrostis stolonifera, Anthoxanthum odoratum, Danthonia decumbens, Deschampsia flexuosa, Festuca ovina, Festuca rubra, Festuca vivipara, Molinia caerulea, Nardus stricta, Blechnum spicant, Pteridium aquilinum