River Avon & Avon Valley
The River Avon and its major tributaries are some of the finest chalk rivers in Europe and support a wide range of fish, bird, mammal and plant species. They are designated as:
- Special Area of Conservation for its watercourse habitat characterised by water crowfoot, and populations of Atlantic salmon, bullhead, brook and sea lamprey, and Desmoulin's whorl snail.
- Special Site of Scientific Interest, supporting important biodiversity action plan species and habitats such as otter, water vole, wet woodland and reed beds.
The Avon Valley includes one of the largest expanses of unimproved floodplain grazing marsh in Britain. It is designated as:
- Special Protection Area for gadwall and Bewick's swan.
- The Special Site of Scientific Interest floodplain grazing marsh supports a complex mosaic of wetland habitats, breeding waders and wintering wildfowl
- Notable for a wide range of breeding wetland birds, rare plants and wetland insects.
The River Avon Special Area of Conservation (SAC) and the Avon Valley Special Protection Area (SPA) are designated for the internationally important features described below.
Watercourse habitat
River habitat characterised by plant communities including water crowfoot and starwort is widespread and varied across Europe. These plant communities provide important habitat and influence flow, nutrient and sediment dynamics.
STREAM river restoration will create more suitable habitat for the plant community by increasing flow speed and cleaning gravels.
Atlantic salmon
Atlantic salmon are widespread in Britain, however their numbers have significantly declined in recent years, with a widespread and sudden decline since 1990. The reasons for the decline include poor survival rates of adults whilst at sea and low egg survival rates due to siltation. The Atlantic salmon in the Avon are thought to be the only remaining genetically pure southern chalk stream population in the UK, as no major stocking has been carried out.
STREAM will create suitable habitat for breeding and for young salmon and develop guidance on measures to reduce entrapment and facilitate fish passage.
Bullhead
Bullhead (sometimes known as Miller's thumb) are found throughout the British Isles but are rare across Europe. These charismatic little fish are easily identified by their large head (up to a quarter of their body length) and camouflaged body. Adult bullhead are very territorial and the males protect their nests by creating clicking sounds.
STREAM will improve habitat for bullhead by developing ways to introduce and retain woody debris.
Brook lamprey
Lamprey belong to a small but rare group of the most primitive of all living vertebrates-jawless fish. They are not true fish, as instead of jaws they have a round sucker-like disc containing strong rasping teeth. Brook lamprey are found throughout most of the Avon system, both at lower densities than expected.
As soon as brook lamprey hatch from eggs, the juveniles drift downstream and burrow into stable silt beds, where they remain for up to seven years. On emerging they create a nest in clean gravels by moving stones with their mouths-hence the origin of lamprey, which means "stone sucker".
STREAM will contribute to the sensitive management of ditch networks for young lamprey and will provide spawning habitat.
Sea lamprey
Sea lamprey have a similar life cycle to brook lamprey but spend their adult years at sea. As juveniles, they spend up to five years hidden in silt beds before they emerge and migrate to the sea. There they use their circular rows of teeth to latch onto and feed on fish before returning to freshwater to spawn. When nesting they use their mouths to move stones heavier than their own body weight, working in teams if necessary.
STREAM will contribute to the sensitive management of ditch networks and will provide spawning habitat for sea lamprey.
Desmoulin's whorl snail
The number of Desmoulin's whorl snail varies throughout the Avon system. The tiny snail is found in vegetation fringing watercourses, and in adjacent wetland habitats. The snails need humid conditions and are found only where water is close the surface. During the warmer part of the year they climb and feed on the leaves of tall wetland plants, before retreating into the leaf litter in winter.
STREAM river restoration will increase the availability of habitat for Desmoulin's and work with the Living River to remove invasive plant species, which threaten its habitat.
Bewick's swan
Bewick's swans are the smallest swans to migrate to Britain. They are named after Thomas Bewick, an illustrator who produced many fine drawings of them. Bewick's swans overwinter in the wet pastures, stillwater and floodplain grasslands of the Avon Valley. The wintering population is declining, in part due to inappropriate water level management and decline of traditional agricultural practices.
STREAM will contribute to more appropriate water level management in the Avon Valley by developing hatch operating protocols and a ditch restoration programme.
Gadwall
Gadwall are a scarce breeding bird and winter visitor to the Avon, inhabiting wet grassland, marshes and lakes with dense fringing vegetation. Most existing areas of habitat for this species are in poor condition due to inappropriate management and/or human disturbance. Gadwall are one of the "dabbling ducks", so called because they put their tails in the air and dip forwards to feed.
STREAM will contribute to more appropriate water level management in the Avon Valley and increase understanding if the effect of human disturbance.