Severn Estuary/ Môr Hafren SAC

Status: Designated


Site overview

The Severn Estuary is the largest coastal plain estuary in the UK with extensive mudflats and sandflats, rocky shore platforms, shingle and islands. Saltmarsh fringes the coast, backed by grazing marsh with freshwater and occasional brackish ditches. This Special Area of Conservation, a type of Marine Protected Area was established to protect this special estuary. Over 100 species of fish call this area home including several rare species, such as the river lamprey, sea lamprey and twaite shad. The river and sea lamprey are a primitive type of fish having a distinctive suckered mouth but no jaws. Although numbers of lamprey have declined over the last 100 years, the UK is still one of their strongholds. They spend their adult life in the sea or estuaries but spawn and spend the juvenile phase in rivers. They use the Severn Estuary as a migratory passage to and from the sea. The Severn Estuary also has the largest eel run in Great Britain.

MPA Type

Special Area of Conservation

Special Areas of Conservation (SACs) are strictly protected sites designated under European legislation. They contribute both to the UK MPA network and set up to protect habitat types and species considered to be most in need of conservation at a European level (excluding birds).

Designation date

1 August 2007

Surface Area

737.63 km2 (284.80 mi.2)


295.89 km (183.86 mi.)

  • Sea lamprey (Petromyzon marinus)

    A primitive jawless fish that looks a bit like an eel.

  • Twaite shad (Alosa fallax)

    Sometimes called a ‘May fish’ as it returns to fresh water to breed in the spring, the twaite shad is a member of the herring family.

  • Atlantic salt meadows (Glauco-Puccinellietalia maritimae)

    Areas with specially adapted plants found in the upper reaches of saltmarshes that are not always reached by the tide. The habitat is used for grazing, but is also very important for birds.

  • Estuaries

    The downstream part of a river, where it nears the sea, which is influenced by the tide These complex habitats can include areas always submerged by the tide as well as those exposed at low tide. They can be exceptionally important feeding and breeding ar

  • Intertidal mudflats and sandflats (Mudflats and sandflats not covered by seawater at low tide)
  • Subtidal sandbanks

    Sandbanks which are slightly covered by sea water all the time

  • Reefs

    Areas where the bedrock, stable boulders and cobbles or structures created by animals arise from the surrounding seabed. They attract and provide a home to a huge variety of plant and animal life.

Did you know?…

To the shelf limits, Scotland has 61% of UK waters, of which 23% are now in existing or new ‘marine protected areas’

An area over 9 times the size of Wales is now in marine protected areas in the UK, but less than 1% is considered by MCS scientists to be well managed