River Parrett - Ecology

Ecology

The river flows through several areas of ecological interest and supports a variety of rare and endangered species.

From January until May, the Parrett provides a source of European Eels (Anguilla anguilla) and young elvers, which are caught by hand netting as this is the only legal means of catching them. A series of eel passes have been built on the Parrett at the King's Sedgemoor Drain to help this endangered species; cameras have shown 10,000 eels migrating upstream in a single night. The 2003 BBC Radio 4 play Glass Eels by Nell Leyshon was set on the Parrett.

To the north of the river bank northwest of Langport are the Aller and Beer Woods and Aller Hill biological Sites of Special Scientific Interest (SSSI). Aller and Beer Woods is a Somerset Wildlife Trust reserve. It consists of large blocks of semi-natural ancient woodland along the west-facing slope of Aller Hill, overlooking King's Sedgemoor. The reserve is about 40 hectares (99 acres) and the underlying geology of most of it is Lias limestone. Prior to the 20th century it appears to have been managed for centuries as traditional coppice woodland, and provides an outstanding example of ancient escarpment woodland. The woodland is a variant of the Calcareous Ash/Wych Elm stand-type, with Pedunculate Oak (Quercus robur), and Ash (Fraxinus excelsior) the dominant canopy trees throughout, and with scattered concentrations of Wych Elm (Ulmus glabra). Ancient woodland indicators include Small-leaved Lime (Tilia cordata), and Wild Service Tree (Sorbus torminalis), both of which are locally common. Plants of particular interest include Bird's Nest Orchid (Neottia nidus-avis), Greater Butterfly Orchid (Platanthera chlorantha) and the very rare Red Data Book species Purple Gromwell (Lithospermum purpurocaeruleum). Aller Hill contains three species of plant which are nationally rare and a further three which are of restricted distribution in Somerset. The central area contains a sward dominated by Sheep's Fescue (Festuca ovina) in combination with Yellow Oat-grass (Trisetum flavescens) and Quaking-grass (Briza media). Salad Burnet (Sanguisorba minor) forms a major component of the sward with the two nationally rare species Rough Marsh-mallow (Althaea hirsuta) and Nit-grass (Gastridium ventricosum), also present.

Southlake Moor is another SSSI, which forms part of an extensive grazing marsh and ditch system. When conditions in the River Parrett are suitable, the moor can be deliberately flooded in winter by opening a sluice in the river's floodbank. Some 96 species of aquatic and bankside vascular plant species have been recorded on Southlake Moor, including the Greater water-parsnip (Sium latifolium). When the moor is flooded it can be occupied by large numbers of wildfowl; up to 22,000 Wigeon (Anas penelope), 250 Bewick's Swan (Cygnus bewickii) and good numbers of Pochard (Aythya ferina), Teal (Anas crecca) and Tufted Duck (Aythya fuligula). Signs of European Otters (Lutra lutra) are regularly seen on the muddy banks of the River Parrett. The ditches on the east side of the site are populated by Palmate Newts (Triturus helveticus).

Langmead and Weston Level is nationally important for its species-rich neutral grassland and the invertebrate community found in the ditches and rhynes. The terrestrial and aquatic invertebrates recorded on the site include four nationally rare species: the Great Silver Diving Beetle (Hydrophilus piceus), the soldier fly Odontomyia ornata, which is now called the Ornate Brigadier, and two other flies, Lonchoptera scutellata and Stenomicra cogani.

The Parrett then flows through the Somerset Levels National Nature Reserve which contains a rich biodiversity of national and international importance. It supports a vast variety of plant species, including common plants such as Marsh Marigold (Caltha palustris), Meadowsweet (Filipendula ulmaria) and Ragged Robin (Lychnis flos-cuculi). The area is an important feeding ground for birds including Bewick’s Swan (Cygnus columbianus bewickii), Eurasian Curlew (Numenius arquata), Common Redshank (Tringa totanus), Skylark (Alauda arvensis), Common Snipe (Gallinago gallinago), Common Teal (Anas crecca), Eurasian Wigeon (Anas penelope) and Whimbrel (Numenius phaeopus), as well as birds of prey including the Western Marsh Harrier (Circus aeruginosus) and Peregrine Falcon (Falco peregrinus). A wide range of invertebrate species is also present including rare insects, particularly the Hairy Click Beetle (Synaptus filiformis) which until recently was only known in Britain from the Parrett, and other insects, including the Lesser Silver Water Beetle (Hydrochara caraboides), Bagous nodulosus, Hydrophilus piceus, Odontomyia angulata, Oulema erichsoni and Valvata macrostoma. In addition, the area supports an important European Otter (Lutra lutra) population. Two-hundred-eighty-two American Mink (Mustela vison) have been captured, after their escape from breeding farms which is encouraging Water Voles (Arvicola amphibius) to recolonise areas of the Levels where they have been absent for 10 years. The Levels and Moors include 32 Sites of Special Scientific Interest (twelve of them also Special Protection Areas), the Huntspill River and Bridgwater Bay National Nature Reserves, the Somerset Levels and Moors Ramsar Site covering about 86,000 acres (348 km2), the Somerset Levels National Nature Reserve, Shapwick Heath National Nature Reserve, and numerous Scheduled Ancient Monuments. In addition, some 72,000 acres (290 km2) of the Levels are recognised as an Environmentally Sensitive Area, while other portions are designated as Areas of High Archaeological Potential. Despite this, there is currently no single conservation designation covering the entire area of the Levels and Moors.

On the outskirts of Bridgwater at Huntworth the river passes the Screech Owl local nature reserve where flooded clay pits provide a roost for thousands of Common Starlings (Sturnus vulgaris) each winter. The mouth of the river is where it flows into the National Nature Reserve at Bridgwater Bay on the Bristol Channel. It consists of large areas of mud flats, saltmarsh, sandflats and shingle ridges, some of which are vegetated. It has been designated as a Site of Special Scientific Interest since 1989, and is designated as a wetland of international importance under the Ramsar Convention. The risks to wildlife are highlighted in the local Oil Spill Contingency Plan.